Add streams to onboard mode

Companion computer interface: Add SYS_COMPANION parameter. Setting it to 921600 enables the companion interface.

NuttX configs / build options: Do not warn about sign compare, as there are a bunch of non-standard signedness assumptions

turn on -Werror and fix resulting errors

Integrate the Google Test framework.

MC pos control offb: read altitude sp separately

add interrupt latency printout and mean/variance to interval perf counter

Geofence parse fix

DO_JUMP feedback in QGC

Improve README