Added basic context structure
Moved data gathering to the model
Merge branch 'mercury' into HG-102

Conflicts:
	extensions/wikia/MercuryApi/MercuryApiController.class.php
Added unit test
Missing new line
Switched to array_column
Reverted getArticleCategoriesTitles; Firxed test formatting
Renamed $article to $articleAsJson
Merge pull request #4567 from Wikia/HG-102

HG-102: Added basic context structure