We assume that recording is supposed to happen on the edges of presses
since otherwise it is very hard to input a sequence without a lot of repeats.

Also we added the feature to continue playing in the background as a drum
computer (with limited accuracy for now as we're using micropython callbacks).

Other things:
- updated bl00mbox use to new API
- added a get_help() method for the onboard help viewer
- reset LEDs when petals are released

This bumps the version to 14.