Feature update - Wavetable ADSR and params, settable synth key colors

Features

• Go to the Wavetable synth settings popup to set ADSR, Sustain, Cutoff filter.
• These parameters are saved once edited but will appear as zeroed until edited
• Map any param to 3D control
• Grab a synth key, click the 'i' to show the colour editor cube. Grab the trigger and move your hand around the RGB cube to set the key colour. Synth key colours are saved in custom layouts.

Fixes

• Fixed save on exit of custom synth key positions
• Fixed lite/demo only allowing one synth when step sequencer controlling synth
• Fixed wavetable pitch bend sticking on -2 after restoring a synth from save and using the pitchbend from 3D control.