Implementation of compute_stable_poses

[clemense]

Shouldn't len(mesh.faces) in https://github.com/mikedh/trimesh/blob/52fded0ada210358dacef8a8b1de82d71615ade6/trimesh/poses.py#L102 be len(cvh.faces)?

[mikedh]

Hey, not totally sure. It looks like it should probably hit that len(nodes) > 0 check first and the len(mesh.faces) is just there as a sanity checking max-iter that's larger than they think the order of magnitude is?

@mmatl PR'd that a while back he might have more insight.