New UML metamodel implementation almost done

Still missing:
- Forward methods for inherited properties and operations
- Auto-removal of deleted composite properties
- Moving documentation from internal do QObject-based classes

Change-Id: I2676e48c53d9ad4cdc6333c28e1a912d4e72cdd0
Reviewed-by: Sandro S. Andrade <sandroandrade@kde.org>