made UserLoginSpecialController::$username and UserLoginSpecialController::$password private
small refactoring
Merge branch 'dev' into CONN-2
new helper method getMainPagePartialUrl() and unit test for getReturnToFromQuery()
refactored getReturnToFromQuery()
added helper method UserLoginSpecialController::isTitleBlacklisted(), fixed testGetReturnToFromQuery() unit test and added new one: testGetReturnToQueryFromQuery()
added one more usecase to data providers, changed name of array keys in getReturnToQueryFromQueryDataProvider()
Merge pull request #2418 from Wikia/CONN-2

CONN-2 Clean up in UserLogin after the issue during the time when fastly was down