Updated the Bullet/Demos/SerializeDemo to load .bullet files with the softbody data.
BulletSoftBody should use getWorldTransform and not getInterpolationWorldTransform
Fix btBulletWorldImporter so that it creates a copy of the index/vertex data, this prevents crashes when deleting the .bullet file with triangle meshes.
Serializes soft body nodes (vertices), links, faces, tetrahedra, materials, anchors with rigid bodies.
Some todo's are serialization of pose, constraints between soft bodies
