Update test_universal to use the new ChLinkUniversal joint.
Update test_universal to use the new ChLinkUniversal joint.

Other changes:
- modify visualization assets to represent the joint's cross element (and visualize satisfaction of the perpendicularity constraint)
- add option to save data for PovRay post-processing
- different set of test configurations

hsu/chrono-vehicle,hsu/chrono-vehicle,hsu/chrono-vehicle