Add second control board (pin limit)

[Jonny999999]

Problem:

not enough gpio pins available -> second pcb?

Idea

• board1:
  • control motors, fan
• board2:
  • send motor commands to board 1
  • handle inputs: stick, sensors, display

[Jonny999999]

Done in V2.1 (see tag)

However approach currently dropped due to switch to other motor driver requiring way fewer pins