BlueOS thruster extension

[EliotBR (Eliot)]

@jwenger

if you use this method you are no longer able to read values coming from an rc receiver using the RC_CHANNELS message.

Alternatively you could use the DO_SET_SERVO approach described here. Note that both this and the RC_CHANNELS_OVERRIDE approach bypass the autopilot for motion control, which also means they bypass its failsafe mechanisms.