Clear calibration method

[francesco-romano]

The calibration phase is not fully documented by Xsens.
For the Codyco demo we try to have an acceptable calibration, but we should properly investigate this issue in the future.

Two points in the calibration:

• what calibrationPose() returns? Is the returned pose really meaningful to be plotted by a visualizer?
• More than one trial to calibrate the suit seems to lead to 'Unknown' calibration result. Furthermore given the current workflow, what is the meaning of the abortCalibration() function?

In practice: how the calibration state machine work?