Implement webm thumbnail replacement.

Conflicts:
	LICENSE
	builds/4chan-X-beta.user.js
	builds/4chan-X.user.js
	src/General/css/style.css
	src/Images/AutoGIF.coffee
	src/Images/Gallery.coffee
	src/Images/ImageLoader.coffee
Clear event listener

Conflicts:
	builds/4chan-X-beta.user.js
	builds/4chan-X.user.js
Pause off screen and better clone handling for GIF/WebM etc. replacement
fix bug in WebM resetting