URDF, SDF, MJCF Model Loading

Hey all,

I am curious if support exists, or will in the future, for the loading of URDF, SDF and/or MJCF model files into nphysics. This functionality would make nphysics highly desirable for simulating robotics and help Rust expand into the robotics world in general. This is something I could potentially help with if there agreement to support such model files.

Perhaps the library is still too young in that it is missing a large variety of joint types, motor types, and sensor types etc,. to make URDF loading of models feasible.