The appendCategory(ConfigCategory*) allows to add a category created by e.g. an Instantiator that can use bindings rather than fixed arguments.
The removeCategory methods allow to remove a category when e.g. the model in an Instantiator resets.

CCBUG: 372090

Pre-requisite for dynamically showing and hiding calendar plugin config in digital clock.

Verified that onObjectAdded and onObjectRemoved of an Instantiator work fine with ConfigModel.

Adding an overload shouldn't cause issues as the others require at least four string arguments.