Ticket #263: Fixed usages of CREATE_CONNECTION_GROUP permission throughout.

guacamole-ext/src/main/java/net/sourceforge/guacamole/net/auth/permission/SystemPermission.java

@@ -61,6 +61,11 @@ public class SystemPermission implements Permission<SystemPermission.Type> {
          */
         CREATE_CONNECTION,
 
+        /**
+         * Create connection groups.
+         */
+        CREATE_CONNECTION_GROUP,
+
         /**
          * Administer the system in general, including adding permissions
          * which affect the system (like user creation, connection creation,