kill register_appobject_class method, simplifying autoregistration. Update test accordingly (test which manually registers object should also properly call there __register__ method). Drop the disable-appobjects config file entry: no one used it since its introduction years ago.

0.0.2: 2.3.0
0.0.3: 2.4.0
# missing 0.0.4 entry, that's alright
0.1.0: 2.6.0
0.1.2: 2.10.0