Add nanoKONTROL2 support

[jmuheim]

TODO:

• nanoKONTROL2 support :-) but not needed in any way, only when connected
• Control groups
  • Groups 1-4: master group's loops
  • Groups 5-8: current group's loops
  • Knob: position on stereo spectrum (should somehow reset to center, or just add/subtract relative value of current position)
  • Slider: volume (should somehow reset to 50%, or just add/subtract relative value of current volume)
  • Solo: play solo
  • Mute: mute
  • Record: Could toggle between functions of controls, e.g. make knob&slider control high/low pass filter
• Other controls: ???