[ConfigModel] Allow programmatically adding and removing ConfigCategory

Authored by broulik on Aug 31 2017, 12:29 PM.

Description

[ConfigModel] Allow programmatically adding and removing ConfigCategory

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

Differential Revision: https://phabricator.kde.org/D7602