Add a "blacklist mode" for all filtering (i.e. inverted whitelist)

@dnovitskyi commented on [Sat Apr 14 2018](https://github.com/AdguardTeam/AdguardForWindows/issues/2175)

As reported by a user #1824528,

> I only use AdGuard on a site or two - is there a setting that will allow me to 'turn it on' for these specific sites and have it 'off' as default mode?

As far as I can understand, he would like AdGuard to have a mode that will allow all ads by default and only block ads on user-specified sites - such as "blacklist" HTTPS filtering mode we already have on Android.

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@ameshkov commented on [Sat Apr 14 2018](https://github.com/AdguardTeam/AdguardForWindows/issues/2175#issuecomment-381289367)

This is possible in the browser extension, this mode is called "inverted whitelist".

However, we don't have it in the premium AG (not many people request it)