Add UrlGeneratorInterface; move logic to *File classes

- Add UrlGeneratorInterface
- Add type hint to ImageServing::getVignetteUrl to require
	UrlGeneratorInterface
- Moved from* logic to File and Global file from VignetteRequest
Fix namespace addressing
Fix image serving namespace
Reorganize VignetteRequest and UrlGeneratorInterface

Move VignetteRequest to includes/wikia/vignette
Move UrlGeneratorInterface to includes/wikia/vignette

/cc @nmonterroso
Merge pull request #5676 from Wikia/urlgeneratorinterface

Add UrlGenerator Interface