Special roles and their methods on GroupTypeInterface have been removed

The special group roles Anonymous, Outsider and Member which could previously not be deleted and were always present for any group type are now no longer like that.

When setting up a group type you can choose to have these be created automatically for you, but you no longer need them. You can delete them if you wish or if you accidentally deleted one you can simply recreate one from the group role form. This means that the methods getAnonymousRole() and similar ones have been removed from GroupTypeInterface.