RigidBodyPhysics TODO

From H3D.org

• Change the way adding forces works. We need to add the same force after each simulation tick so we need to collect the calls in addLocalExternalForce, etc and execute them after each simulation tick. As it is now several simulation ticks is run without any force input.
• Maybe make a Capsule geometry since it is available in ODE, Bullet and PhysX
• Joints - ensure a RigidBody with fixed value true does not move
• Offset forces affecting rigidbody with the Collidable shapes translation and rotation fields.