Qualisys example script sensitive to errors when pushing full pose

[krichardsson]

The https://github.com/bitcraze/crazyflie-lib-python/blob/master/examples/qualisys/qualisys_hl_commander.py script gets the full pose from the QTM and pushes it into the Crazyflie using the send_extpose() function of the Extpos class in the python lib. For unknown reasons, the script seems to be sensitive to errors in the pose, resulting in a CF that flips or go in the wrong direction. It very much looks like the estimated position in the CF is wrong.

There are lots of possible error sources:

• Unexpected data from the Qualisys system
• A bug in the script when pushing the pose
• The std used when pushing the pose into the EKF might be off
• A bug in the firmware handling pose data
• Delays

This requires more investigations.

Using only the position works fine (through the send_extpos() method).

[knmcguire]

#305 was perhaps related to this, but let's see.

It would perhaps be good to implement this python library of libmotion capture instead as that is more often tested?

https://github.com/IMRCLab/libmotioncapture

I mentioned this in the cfclient issue: bitcraze/crazyflie-clients-python#577

[knmcguire]

In Crazyswarm(2) the variance of the external position is adjusted by standard before pushing the mocap results to the EKF. So we need to do that in this script as well.