The downside of this is that the functions are now virtual, which makes
them slower than before. Maybe final qualifier would help?
AbstractObject::sceneObject() is marked as private in Object to avoid
confusion.
Functionality present in Object is now split into three main components:
* Object itself, handling parent/children relationships
* Transformation implementation and interfaces for common functionality
* Object features, providing transformation caching and base for
cameras, collision shapes, rigid bodies etc.
Some functionality depending on former implementation is temporarily
disabled and will be reworked later.