Add access to attitude rates

[cheintz]

This seemed to be a good place for them, as they come in the Attitude MAVlink packet.

Resubmitting after rebasing on dronekit:master

[peterbarker]

I think we should have separate objects and accessors for the rotation rates.

We don't conflate position and its first derivation velocity, so I can't see why we'd want to do it for attitude.

So basically an AttitudeRate object.

Does that make sense?

Ah, the argument "that's how MAVLink does it" isn't a great one, either. MAVLink (and its implementations) gets lots of stuff wrong, and dronekit-python is supposed to kinda fix these things :-)

[hamishwillee]

FWIW Yes to an AttitudeRate object. Would be good if during implementation this could be added to the vehicle_state.py as the absolute bare minimum test.

[amilcarlucas]

@cheintz any progress on this ?