(Bring back) ULX support

[Linus045]

In Commit 8961adb ULX support was removed in favor of the buddy/blocked player system.
However it would be nice to have the ability to use ULX's permission system to handle access.
That way server admins can easily edit permissions for single players or groups.

In addition to the current 4 permission settings there should be a 5th option, one which allows access only via ULX's permission system, although the ability to block players should still be given to prevent abuse.