Add session segments for the time syncronization periods

[moorepants]

We have session segments, "trials", for "static" and the different surfaces but it would be helpful to have the time synchronizations labeled too. The periods where you move the stroller/bike back and forth to register the same longitudinal acceleration in all sensors. I would like to add a check in the data processing pipeline that verifies if the signals seem to be synchronized in time.

This can be done in January, it isn't super critical for the draft report.

[moorepants]

Not all trials have the time synchronization motion labeled in the events files. Here is a list:

• session001
• session002
• session003
• session004
• session005
• session006
• session007
• session008
• session009
• session010
• session011
• session012
• session013
• session014: shaking sensor trial
• session015
• session016
• session017
• session018
• session019
• session020
• session021
• session022

[GabrieleDello]

Session014 is a test of taping IMUs together and shaking them.