[qutebrowser] Extend ad blocking to allow single URL blocking.

[Viacheslav Chimishuk]

> Sounds great. The Compiler is currently working on a plugin system,
> which I believe would make this even easier to implement. If I recall
> correctly, even the current hostblocking would be extracted to a plugin
> so we could just extend that to include the functionality you
> described.

Yeah, it is relatively simple change. After the whole adblock.py can
be migrated to a plugin framework. This is the plan.

--
Best regards, Viacheslav Chimishuk
vchimishuk at yandex.ru
Ukraine, Khmelnitsky