ArticlesApiController: PHP hinting
ImageServingController: use JSON format by default
ImageServing: cache images with maximum limit

ImageServing::getImages() will take a slice when getting data from cache
ImageServing: mark getThumbnails() as deprecated
Merge branch 'dev' into bac-734-image-serving-results-caching

Conflicts:
	extensions/wikia/ImageServing/drivers/ImageServingDriverBase.class.php
	extensions/wikia/ImageServing/drivers/ImageServingDriverUserNS.class.php
Merge pull request #1443 from Wikia/bac-734-image-serving-results-caching

BAC-734 Image Serving results caching