PLAT-532 Replace File::createThumb thumbnail using vignette

This is a follow-on to https://github.com/Wikia/app/pull/5118 and https://wikia-inc.atlassian.net/browse/PLATFORM-513.

The right rail photo module links to `/Special:NewFiles`. This PR addresses the thumbnail generation there.

Replace File::createThumb thumbnail generation using vignette and surround the new thumbnail generation with a `wgEnableVignette` block so it will be toggled when vignette is enabled.

https://wikia-inc.atlassian.net/browse/PLATFORM-532

/cc @nmonterroso