#22 Rigid Constraints

[Matt Wash]

Panos has created some cool hinged boxes and spheres that we can use to test Sam's RigidConstraint metadata code. i think this is unfinished because the collada spec is super-complicated relating to this area. Now we have some collada examples, it might be easier to see how things work. Once the rigid constraints have been read in from the collada file, we then have to create them in the Bullet physics world.