AssetsManager: add isGroupUrl and getGroupNameFromUrl methods
WallNotifications: load AM group instead of a single group
WikiaSkin: introduce getScriptsWithCombinedGroups method (CON-1772)
Venus: use WikiaSkin::getScriptsWithCombinedGroups to generate both bottom JS requests and inline bottom scripts
Add test for WikiaSkin::getScriptsWithCombinedGroups
RelatedPages: improve the way JS group is loaded
Merge branch 'CON-NewArticle' into con-1772-combine-am-js-requests
AssetsManager: improve performance of loading config groups
AssetsManager: use shared AssetsConfig + throw AssetsManagerException when not existing group is requested
WikiaException: log "real" class of the exception + logging for dev environment
RelatedPages: not needed on Venus

This reverts commit 7a8d27a95442a3807557b0584ab309b345838b9e.
Merge pull request #5139 from Wikia/con-1772-combine-am-js-requests

CON-1772: combine AssetsManager JS requests