Release: Loop Subdivision

[mikedh]

• release Add loop subdivision algorithm #1750
• test and fix Improperly read body name in multi-body ASCII STL file #1761 albeit in a non-case-sensitive way.
• release feature: Support adding animations to GLTF export as a postprocessing step #1765
• fix Convert DAE with multiple materials to OBJ #1755 by combining materials on OBJ export
• remove the split_object argument from load_obj and rewrite the obj face preprocessing logic.
• add upstream URDF schema for exports that we don't pass. I'm not sure if we should support either more or less of the URDF format.