Trim/cut/resize operations on trial

[Alzathar]

In BTK, a btk::Acquisition has the possibility to resize it number of samples from the beginning and the end. We can do the same for a ma::Trial object.

In fact, we can do more as proposed on the forum: How to properly cut/resize/trim a trial?

• ma::processing::trim(): remove all the samples at the beginning and the end of trial where reconstructed time sequences has residual < 0
• ma::processing::cut(): split the trial into several ones
• ma::processing::resize(): set the number of frame for each time sequence in a trial (starting from the begging or the end of the data)