UR10 uses complex collision meshes

[William Woodall]

It would be good to approximate the collision of the UR10 arm using primitive shapes rather than the UR10's visual mesh (which appears to be the case). The default behavior should be preserved, with an option to switch our prefered simpler collision meshes. That way we can propose it as an improvement upstream.

[Brian Gerkey]

Check upstream first to see if it's been done already.