Apply /* @embed */ pragma to every image, not just the topmost in each block

ResourceLoader's CSSMin scopes each /* @embed */ to the rule immediately below
it, not the entire block. This patch adds the pragma for the image assets
which were omitted.
Merge pull request #124 from atdt/master

Apply /* @embed */ pragma to all images, not just the topmost in each block
Drop -moz-linear-gradient for images

The costs are bigger than benefits now
Merge pull request #125 from Nikerabbit/linear-gradient

Drop -moz-linear-gradient for images
Localisation updates from https://translatewiki.net.
Add rwr and ota to the languages supported by ULS

Issue: #126
Downstream bug: https://bugzilla.wikimedia.org/show_bug.cgi?id=60815