Can't download new board support behind proxy

I can't download new board support behind a proxy, using Arduino 1.8.10 under Ubuntu 18.04 LTS.

I'm behind my university's proxy that uses authentication.

First I tried the automatic proxy setup with the according script which fails the same way as using the manual http proxy setting to download the `package_index.json`:

```
2019-10-21T13:45:31.765Z DEBUG c.a.u.n.HttpConnectionManager:125 [cc.arduino.packages.discoverers.serial.SerialDiscovery] Using proxy HTTP @ proxy.hs-karlsruhe.de/193.196.64.2:8888
2019-10-21T13:45:32.185Z INFO c.a.u.n.HttpConnectionManager:148 [cc.arduino.packages.discoverers.serial.SerialDiscovery] Connect to https://builder.arduino.cc/builder/v1/boards/0x8087/0x0AB6, method=GET, request id=34F2F0F71F254597
2019-10-21T13:45:32.242Z WARN p.a.h.BoardCloudResolver:79 [cc.arduino.packages.discoverers.serial.SerialDiscovery] Error during get board information by vid, pid
java.io.IOException: Unable to tunnel through proxy. Proxy returns "HTTP/1.0 407 Proxy Authentication Required"
at sun.net.www.protocol.http.HttpURLConnection.doTunneling(HttpURLConnection.java:2142) ~[?:1.8.0_191]
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:183) ~[?:1.8.0_191]
at sun.net.www.protocol.https.HttpsURLConnectionImpl.connect(HttpsURLConnectionImpl.java:162) ~[?:1.8.0_191]
at cc.arduino.utils.network.HttpConnectionManager.makeConnection(HttpConnectionManager.java:150) ~[arduino-core.jar:?]
at cc.arduino.utils.network.HttpConnectionManager.makeConnection(HttpConnectionManager.java:112) ~[arduino-core.jar:?]
at processing.app.helpers.BoardCloudResolver.getBoardBy(BoardCloudResolver.java:61) [arduino-core.jar:?]
at cc.arduino.packages.discoverers.serial.SerialDiscovery.forceRefresh(SerialDiscovery.java:204) [arduino-core.jar:?]
at cc.arduino.packages.discoverers.serial.SerialDiscovery$1.run(SerialDiscovery.java:97) [arduino-core.jar:?]
at java.util.TimerThread.mainLoop(Timer.java:555) [?:1.8.0_191]
at java.util.TimerThread.run(Timer.java:505) [?:1.8.0_191]
2019-10-21T13:45:39.745Z INFO c.a.c.p.ContributionInstaller:305 [ContributionManager Update Thread] Start download and signature check of=[https://downloads.arduino.cc/packages/package_index.json]
2019-10-21T13:45:39.763Z INFO c.a.u.n.FileDownloaderCache:92 [ContributionManager Update Thread] Cache folder /home/client1ubuntu/.arduino15/cache
2019-10-21T13:45:39.854Z INFO c.a.u.n.FileDownloaderCache:149 [ContributionManager Update Thread] Get file cached is expire true, exist false, info FileCached{eTag='null', lastETag='null', remoteURL='https://downloads.arduino.cc/packages/package_index.json', localPath='/home/client1ubuntu/.arduino15/cache/downloads.arduino.cc/packages/package_index.json', md5='null', createdAt='2019-10-21T15:45:39.804', cacheControl=null}
2019-10-21T13:45:39.859Z DEBUG c.a.u.n.HttpConnectionManager:125 [ContributionManager Update Thread] Using proxy HTTP @ proxy.hs-karlsruhe.de/193.196.64.2:8888
2019-10-21T13:45:39.878Z INFO c.a.u.n.HttpConnectionManager:148 [ContributionManager Update Thread] Connect to https://downloads.arduino.cc/packages/package_index.json, method=HEAD, request id=B04AAD63855047CB
2019-10-21T13:45:39.908Z ERROR c.a.u.n.FileDownloader:199 [ContributionManager Update Thread] The request stop
java.io.IOException: Unable to tunnel through proxy. Proxy returns "HTTP/1.0 407 Proxy Authentication Required"
at sun.net.www.protocol.http.HttpURLConnection.doTunneling(HttpURLConnection.java:2142) ~[?:1.8.0_191]
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:183) ~[?:1.8.0_191]
at sun.net.www.protocol.https.HttpsURLConnectionImpl.connect(HttpsURLConnectionImpl.java:162) ~[?:1.8.0_191]
at cc.arduino.utils.network.HttpConnectionManager.makeConnection(HttpConnectionManager.java:150) ~[arduino-core.jar:?]
at cc.arduino.utils.network.HttpConnectionManager.makeConnection(HttpConnectionManager.java:106) ~[arduino-core.jar:?]
at cc.arduino.utils.network.FileDownloaderCache.updateCacheInfo(FileDownloaderCache.java:184) ~[arduino-core.jar:?]
at cc.arduino.utils.network.FileDownloaderCache.getFileCached(FileDownloaderCache.java:153) ~[arduino-core.jar:?]
at cc.arduino.utils.network.FileDownloader.downloadFile(FileDownloader.java:167) ~[arduino-core.jar:?]
at cc.arduino.utils.network.FileDownloader.download(FileDownloader.java:129) ~[arduino-core.jar:?]
at cc.arduino.contributions.DownloadableContributionsDownloader.download(DownloadableContributionsDownloader.java:142) ~[arduino-core.jar:?]
at cc.arduino.contributions.DownloadableContributionsDownloader.downloadIndexAndSignature(DownloadableContributionsDownloader.java:160) ~[arduino-core.jar:?]
at cc.arduino.contributions.packages.ContributionInstaller.updateIndex(ContributionInstaller.java:306) ~[arduino-core.jar:?]
at cc.arduino.contributions.packages.ui.ContributionManagerUI.lambda$onUpdatePressed$1(ContributionManagerUI.java:146) ~[pde.jar:?]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_191]
2019-10-21T13:45:39.913Z ERROR c.a.c.DownloadableContributionsDownloader:176 [ContributionManager Update Thread] Cannot download the package index from https://downloads.arduino.cc/packages/package_index.json the package will be discard
java.lang.Exception: Error downloading https://downloads.arduino.cc/packages/package_index.json
at cc.arduino.contributions.DownloadableContributionsDownloader.download(DownloadableContributionsDownloader.java:144) ~[arduino-core.jar:?]
at cc.arduino.contributions.DownloadableContributionsDownloader.downloadIndexAndSignature(DownloadableContributionsDownloader.java:160) ~[arduino-core.jar:?]
at cc.arduino.contributions.packages.ContributionInstaller.updateIndex(ContributionInstaller.java:306) ~[arduino-core.jar:?]
at cc.arduino.contributions.packages.ui.ContributionManagerUI.lambda$onUpdatePressed$1(ContributionManagerUI.java:146) ~[pde.jar:?]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_191]
Caused by: java.io.IOException: Unable to tunnel through proxy. Proxy returns "HTTP/1.0 407 Proxy Authentication Required"
at sun.net.www.protocol.http.HttpURLConnection.doTunneling(HttpURLConnection.java:2142) ~[?:1.8.0_191]
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:183) ~[?:1.8.0_191]
at sun.net.www.protocol.https.HttpsURLConnectionImpl.connect(HttpsURLConnectionImpl.java:162) ~[?:1.8.0_191]
at cc.arduino.utils.network.HttpConnectionManager.makeConnection(HttpConnectionManager.java:150) ~[arduino-core.jar:?]
at cc.arduino.utils.network.HttpConnectionManager.makeConnection(HttpConnectionManager.java:106) ~[arduino-core.jar:?]
at cc.arduino.utils.network.FileDownloaderCache.updateCacheInfo(FileDownloaderCache.java:184) ~[arduino-core.jar:?]
at cc.arduino.utils.network.FileDownloaderCache.getFileCached(FileDownloaderCache.java:153) ~[arduino-core.jar:?]
at cc.arduino.utils.network.FileDownloader.downloadFile(FileDownloader.java:167) ~[arduino-core.jar:?]
at cc.arduino.utils.network.FileDownloader.download(FileDownloader.java:129) ~[arduino-core.jar:?]
at cc.arduino.contributions.DownloadableContributionsDownloader.download(DownloadableContributionsDownloader.java:142) ~[arduino-core.jar:?]
... 4 more
2019-10-21T13:45:39.918Z ERROR c.a.c.p.ContributionInstaller:308 [ContributionManager Update Thread] Error downloading https://downloads.arduino.cc/packages/package_index.json
java.lang.Exception: Error downloading https://downloads.arduino.cc/packages/package_index.json
at cc.arduino.contributions.DownloadableContributionsDownloader.download(DownloadableContributionsDownloader.java:144) ~[arduino-core.jar:?]
at cc.arduino.contributions.DownloadableContributionsDownloader.downloadIndexAndSignature(DownloadableContributionsDownloader.java:160) ~[arduino-core.jar:?]
at cc.arduino.contributions.packages.ContributionInstaller.updateIndex(ContributionInstaller.java:306) ~[arduino-core.jar:?]
at cc.arduino.contributions.packages.ui.ContributionManagerUI.lambda$onUpdatePressed$1(ContributionManagerUI.java:146) ~[pde.jar:?]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_191]
Caused by: java.io.IOException: Unable to tunnel through proxy. Proxy returns "HTTP/1.0 407 Proxy Authentication Required"
at sun.net.www.protocol.http.HttpURLConnection.doTunneling(HttpURLConnection.java:2142) ~[?:1.8.0_191]
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:183) ~[?:1.8.0_191]
at sun.net.www.protocol.https.HttpsURLConnectionImpl.connect(HttpsURLConnectionImpl.java:162) ~[?:1.8.0_191]
at cc.arduino.utils.network.HttpConnectionManager.makeConnection(HttpConnectionManager.java:150) ~[arduino-core.jar:?]
at cc.arduino.utils.network.HttpConnectionManager.makeConnection(HttpConnectionManager.java:106) ~[arduino-core.jar:?]
at cc.arduino.utils.network.FileDownloaderCache.updateCacheInfo(FileDownloaderCache.java:184) ~[arduino-core.jar:?]
at cc.arduino.utils.network.FileDownloaderCache.getFileCached(FileDownloaderCache.java:153) ~[arduino-core.jar:?]
at cc.arduino.utils.network.FileDownloader.downloadFile(FileDownloader.java:167) ~[arduino-core.jar:?]
at cc.arduino.utils.network.FileDownloader.download(FileDownloader.java:129) ~[arduino-core.jar:?]
at cc.arduino.contributions.DownloadableContributionsDownloader.download(DownloadableContributionsDownloader.java:142) ~[arduino-core.jar:?]
... 4 more
2019-10-21T13:45:39.922Z INFO c.a.c.p.ContributionInstaller:314 [ContributionManager Update Thread] Downloaded package index URL=[https://downloads.arduino.cc/packages/package_index.json]
2019-10-21T13:45:39.924Z INFO c.a.c.p.ContributionInstaller:324 [ContributionManager Update Thread] Check unknown files. Additional package index folder files=[package_index.json], Additional package index url downloaded=[]
```

Then I tried the socks-proxy which worked to download the `package_index.json` but then fails when I try to download the board-support libraries with the error:
```
2019-10-21T14:13:18.100Z INFO c.a.u.n.FileDownloaderCache:131 [ContributionManager Install Thread] The cache is not enable.
2019-10-21T14:13:18.108Z DEBUG c.a.u.n.HttpConnectionManager:125 [ContributionManager Install Thread] Using proxy DIRECT
2019-10-21T14:13:18.109Z INFO c.a.u.n.HttpConnectionManager:148 [ContributionManager Install Thread] Connect to https://github.com/arduino/ArduinoCore-arc32/archive/2.0.3.zip, method=GET, request id=5514BA7A04A14F91
2019-10-21T14:13:23.118Z ERROR c.a.u.n.FileDownloader:194 [ContributionManager Install Thread] The request went in socket timeout
java.net.SocketTimeoutException: connect timed out
at java.net.PlainSocketImpl.socketConnect(Native Method) ~[?:1.8.0_191]
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[?:1.8.0_191]
at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[?:1.8.0_191]
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[?:1.8.0_191]
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[?:1.8.0_191]
at java.net.Socket.connect(Socket.java:589) ~[?:1.8.0_191]
at sun.security.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:666) ~[?:1.8.0_191]
at sun.net.NetworkClient.doConnect(NetworkClient.java:175) ~[?:1.8.0_191]
at sun.net.www.http.HttpClient.openServer(HttpClient.java:463) ~[?:1.8.0_191]
at sun.net.www.http.HttpClient.openServer(HttpClient.java:558) ~[?:1.8.0_191]
at sun.net.www.protocol.https.HttpsClient.(HttpsClient.java:264) ~[?:1.8.0_191]
at sun.net.www.protocol.https.HttpsClient.New(HttpsClient.java:367) ~[?:1.8.0_191]
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.getNewHttpClient(AbstractDelegateHttpsURLConnection.java:191) ~[?:1.8.0_191]
at sun.net.www.protocol.http.HttpURLConnection.plainConnect0(HttpURLConnection.java:1199) ~[?:1.8.0_191]
at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:1050) ~[?:1.8.0_191]
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:177) ~[?:1.8.0_191]
at sun.net.www.protocol.https.HttpsURLConnectionImpl.connect(HttpsURLConnectionImpl.java:162) ~[?:1.8.0_191]
at cc.arduino.utils.network.HttpConnectionManager.makeConnection(HttpConnectionManager.java:150) ~[arduino-core.jar:?]
at cc.arduino.utils.network.HttpConnectionManager.makeConnection(HttpConnectionManager.java:106) ~[arduino-core.jar:?]
at cc.arduino.utils.network.FileDownloader.openConnectionAndFillTheFile(FileDownloader.java:234) ~[arduino-core.jar:?]
at cc.arduino.utils.network.FileDownloader.downloadFile(FileDownloader.java:182) ~[arduino-core.jar:?]
at cc.arduino.utils.network.FileDownloader.download(FileDownloader.java:129) ~[arduino-core.jar:?]
at cc.arduino.contributions.DownloadableContributionsDownloader.download(DownloadableContributionsDownloader.java:142) ~[arduino-core.jar:?]
at cc.arduino.contributions.DownloadableContributionsDownloader.download(DownloadableContributionsDownloader.java:78) ~[arduino-core.jar:?]
at cc.arduino.contributions.DownloadableContributionsDownloader.download(DownloadableContributionsDownloader.java:60) ~[arduino-core.jar:?]
at cc.arduino.contributions.packages.ContributionInstaller.install(ContributionInstaller.java:105) ~[arduino-core.jar:?]
at cc.arduino.contributions.packages.ui.ContributionManagerUI.lambda$onInstallPressed$2(ContributionManagerUI.java:172) ~[pde.jar:?]
at java.lang.Thread.run(Thread.java:748) [?:1.8.0_191]
```

Start with cc.arduino.utils.network.HttpConnectionManager and the download flow through FileDownloader and ContributionInstaller, using the reported authenticated HTTP and SOCKS proxy scenarios. Reproduce the 407 and socket-timeout failures; done means board support and package_index.json downloads work through the configured proxy.

Written by the indexing model from the issue text.