cflib implement notify setpoint stop

[knmcguire]

The notify setpoint stop didn't exist in the cflib before so it was not implemented in crazyswarm2 yet. However, we now have it available in the commander cfilb since the last release. Also this needs to be implemented to the vel_mux teleoperate example since that will no longer take off after on flight.

That latter is also kind of linked to this issue bitcraze/crazyflie-lib-python#419

[knmcguire]

we....might need to implement this for c++ part as well. With the latest release candidate the hello world and such doesn't work anymore with takeoff

[whoenig]

The cpp backend has notifySetpointStop, though?

[knmcguire]

yeah, this is probably not an accurate statement. There is probably something else going on, since the cpp backend doesn't take off at all with the latest master of crazyflie-firmware so I thought it might be related to this (but it probably is not)