Time Offset direction

We curently have two places with time offsets between MoCap and Video data.

PeTrack, which uses

$t_{video} - t_{xsens}$

XSens, which uses

$t_{xsens} - t_{video}$

To reduce confusion, and since we cannot change the C3D file format, we should adapt PeTrack accordingly.

added MoCap usability labels

created branch 400-time-offset-direction to address this issue

mentioned in merge request !287 (merged)

mentioned in commit 8ad5b0d3

closed with merge request !287 (merged)