Unit tests added for wfReplaceImageServer
ThumbnailVideo: rewrite URLs using $wgWikiaVideoImageHost
Merge branch 'dev' into bac-864-video-swift

Conflicts:
	includes/wikia/GlobalFunctions.php
	includes/wikia/tests/ReplaceImageServerTest.php
Merge pull request #1798 from Wikia/bac-864-video-swift

ThumbnailVideo: rewrite URLs