Refactor badaccess-groupX and friends to use User::getGroupsWithPermission().

Refactor badaccess-groupX and friends to use User::getGroupsWithPermission().
* Should be a bit cleaner, and remove those ugly ugly switch() statements.
* Two messages are all that's needed here. Badaccess-group0, a generic "Permission denied" when no group is allowed access; and badaccess-groups which takes two parameters of $1 (groups required for access) and $2 (number of group matches, used for {{PLURAL:}}ing the message).