(CE-767) Make FBConnect user group implicit for ListUsers

Just adding the group to $wgImplicitGroups isn't enough to make the
group actualy implicit and therefore ignored on ListUsers and
elsewhere, it also requires being added to $wgAutopromote.
(CE-767) Include fb-user in no group on ListUsers

Include fb-user in no group on ListUsers when querying the events table.
Merge pull request #3502 from Wikia/CE-767

(CE-767) Make FBConnect user group implicit