GUACAMOLE-220: Add missing definitions for CREATE_USER_GROUP system permission.

guacamole/src/main/webapp/app/rest/types/PermissionSet.js

@@ -142,6 +142,11 @@ angular.module('rest').factory('PermissionSet', [function definePermissionSet()
          */
         CREATE_USER : "CREATE_USER",
 
+        /**
+         * Permission to create new user groups.
+         */
+        CREATE_USER_GROUP : "CREATE_USER_GROUP",
+
         /**
          * Permission to create new connections.
          */