Allow to disable default autopilot PIDs outright

Right now command chip autopilot PIDs cannot be disabled - pitch & rocket yaw is clamped to minimum 10,0,0, and plane roll is clamped to minimum 0.6,0,0.
This especially sucks if you want to make your own autopilot PIDs with Funk and Vizzy, as you must also implement a wholly separate autopilot input system or put up with the chip's PIDs interfering with your own work.