BAC-770: ImageServing

Don't return images that can not be rendered by thumbnailer (i.e. audio, video and SVG)
Swift: enable on all Poznań devboxes, tej!
BAC-770: add unit test
Merge branch 'dev' into bac-770-image-serving-mime-blacklist
Revert "Swift: enable on all Poznań devboxes, tej!"

This reverts commit d80d596f7acca4f9b72ad7d823ca18c0683b35c1.
Merge branch 'dev' into bac-770-image-serving-mime-blacklist
BAC-770: imageServing.php helper script

Show the final list of images as well (after filers being applied)
Merge pull request #1856 from Wikia/bac-770-image-serving-mime-blacklist

BAC-770: add MIME blacklist to ImageServing