create final schematics (with less calibration potis)

[Windfisch]

• [ ] VCO: remove var_vsrc, hard-wire schmitt_feedback and maybe even the tune poti
• [ ] voice board: get rid of all the trim potis; no filter overdrive (vca is enough)
• [ ] main board: figure out how to create the supply voltages
• [ ] put everything together, or at least put voltage converters on each board; or proper power distribution wiring.