vrevent.py: add a Tiltbrush-style drawing example using pybullet
Expose getVREvents to pybullet / shared memory API, access to any VR controller state & state changes.
Improve performance of user debug lines (pybullet/shared memory API) by batching lines with same color/width
expose rayTest to pybullet/shared memory API (single ray for now)
add pybullet getMatrixFromQuaterion