add rolling/spinning friction to cube, remove it from plane/samurai.urdf
URDF2Bullet: support joint limits for revolute and prismatic, only if defined (if upper < lower, disable limit)
add some profiling markers to improve performance
Fix uninitialized variable jointDamping/jointFriction in SDF importer
Add SDF <pose> parsing in visual, inertial, collision elements.
Slight improvement in TinyRender loading performance of largish meshes (30k vertices)
Reduce #define MAX_SDF_BODIES to 500, due to some issue in client code, todo: figure out what the issue is.
b3RobotSimAPI support SDF file loading
Tiny improvement in OpenGL hardware renderer lighting, to distinguish faces without textures