x3dom physics with ammo

1. Based on the RigidBodyPhysics component of the Extensible 3D (X3D), (http://www.web3d.org/files/specifications/19775-1/V3.2/Part01/components/rigid_physics.html), i have registered the rigid body nodes to x3dom (see physics_readme.txt).
2. Now, with the new registered nodes, i am able to use the internal methods (_cf & _vf) to find children and attributes inside them and compare them using x3dom.isa().
3. I have also changed all the math inside the js to the internal x3dom.fields type.