WorldEntity scaling with physics

[rgrieder]

When using physics, it is not possible to scale an object at the moment. The problem is that the Bullet physics engine doesn't support that kind of transformation natively. The main reason is that the collision shapes have fixed size. You create a sphere with radius 5 and will have that radius as long as its lifetime.

But: You can apply setLocalScaling() to every collision shape. The implementation however is not complete. For instance for compound collision shapes, it has no effect. That inevitable means that we need to do some heavy work ourself. Imagine you want to scale a compound collision shape: You will have to scale each and every shape itself and even adjust the transformation.

There is more problems: SphereCollisionShape obviously does not support non-uniform scaling (or it won't be a sphere anymore). You will have to check every bullet collision shapes for its scaling capabilities and implement that in our framework. This can unfortunately only be done by examining the Bullet source code.