static function removeSource($source)
 {
     $permissions = Permissions::findAll(array('conditions' => "`source` = '" . $source . "'"));
     if (is_array($permissions)) {
         foreach ($permissions as $permission) {
             PermissionManager::removeUserPermissions($permission);
             $permission->delete();
         }
         return true;
         // permission source removed
     }
     return false;
     // permission source does not exist
 }