Add learning support for microphone ducking.
Support learning toggle recording, waveform zoom, and set internal sync master.
Turn BPM controls for decks and internal clock into potmeters (allowing out of range sets).

* Allows mapping of a knob to the provided BPM range (1-200).
* Creates _up/_down/_up_small/_down_small helper COs.
* Set step to 1 and small step to 0.1.
Support learning of deck BPM and internal clock BPM.