- Breaking proto updates
- added position nonce to config, and added ability to specify a
sub_position via config as well => more flexibility to control position
via config
- added version as first field of serial protocol messages, so future
breaking proto updates can easily be detected and ignored
- Fixed up web-based demo of a mock video editor/timeline jog/playback
controller
- Fixed config/state flow so that mode changes correctly maintain
playback position
- Demo: https://www.youtube.com/watch?v=J9192DfZplk