Nextcloudcmd: add support for Tor via socks5 proxy

Hi there,

### Expected behaviour

I'm trying to use nextcloudcmd with Tor. For that, I need use a socks5 proxy:

`nextcloudcmd --logdebug --httpproxy socks5://127.0.0.1:9050 /home/amnesia/Persistent/nextcloud https://server.name`

### Actual behaviour

I get the following error message:

[ info nextcloud.sync.accessmanager ]: 2 "" "[...]/ocs/v1.php/cloud/capabilities?format=json" has X-Request-ID "4d7dd[...]"
[ info nextcloud.sync.networkjob ]: OCC::JsonApiJob created for "[...]" + "ocs/v1.php/cloud/capabilities" ""
[ warning nextcloud.sync.networkjob ]: QNetworkReply::NetworkError(UnknownNetworkError) "Error communicating with HTTP proxy" QVariant(Invalid)
[ info nextcloud.sync.networkjob.jsonapi ]: JsonApiJob of QUrl("[...]/ocs/v1.php/cloud/capabilities?format=json") FINISHED WITH STATUS "UnknownNetworkError Error communicating with HTTP proxy"
[ warning nextcloud.sync.networkjob.jsonapi ]: Network error: "ocs/v1.php/cloud/capabilities" "Error communicating with HTTP proxy" QVariant(Invalid)
[ debug default ] [ main(int, char**)::