New plugin : adblock

This plugin aims at blocking images and flash content in feeds (with
either a blacklisting or whitelisting policy). It also allows to delete
images on mobile devices to accelerate downloading of leed pages. The
deleted content can be displayed by clicking on them (click to play).
They can be replaced by same-size elements to keep layout intact.

See README.md in adblock folder for more info.

I tested it with success on some feeds, please report any issue with the
corresponding faulty feed.

This plugin aims at correcting issue #221 in Leed.