Tidy up GPS hold code a little

GPS Position hold, a little tidying

Remove magnetometer PCB, never really started

Add GPS and WIP position hold (without compass)

Rename pitch and roll variables for clarity. The gyro hardware calls the pitch axis X and the roll axis Y which I find confusing.

Make motor mappings and prop configuration much clearer. Improve voltage string handling.

remove copper under inductor

Fix layout for SMPS feedback capacitor

Update README

Nothing of importance in this commit