Updates in response to KVersionControlPlugin interface changes.
Summary:
Updates VCS-plugins for the new KVersionControlPlugin interface. Updates available in the separate commit D29041.
Plugins unversionedActions() functions now do nothing so it doesn't change any current plugin behaviour.
Reviewers: Dolphin, meven, elvisangelaccio
Reviewed By: Dolphin, meven, elvisangelaccio
Differential Revision: https://phabricator.kde.org/D29042