Add new Kit Mode: "Crossfade (volume)".
Fix start phase bug for frequency LFOs.
Finish up most of SUBsynth LFO UI integration and sound.
Add remaining SUBnote LFO params, and use in DSP code.
Convert SUBnote->Envelopes and LFO raw pointers to unique_ptr.
Make messages better for FreeMode points, esp. with MIDI Learn.
Implement MIDI Learn for envelope freemode points.
Fix channel aftertouch using the wrong parameter as basis.