Remove staff only restriction on ajax controller - access control is on entry point (ajax.php) and exposed methods

Fixes for email filtering

Reviewed By: Peter Rotich 07/22/12

Canned Autoresponse

Reviewed By: Peter Rotich 07/22/12

Allow members of a group access to a department

Reviewed-by: Jared Hancock <jared@osticket.com>

And remove unsupported filter of email headers

Change enableGroupMembership() to isGroupMembershipEnabled(). Improve getMembers function. Make sure  is an array in updateAllowedGroups