Export real-time data into convenient format

[pattacini]

For enabling offline reporting of the experiments, it is required to export data acquired in real-time into formats that are general enough for ensuring an appropriate level of post-processing.

We would like to go with https://github.com/tbeu/matio, which guarantees to produce files that are in turn MATLAB/Octave compatible.

[vvasco]

The class Manager uses matio to produce a file where data are appended at every "session". The final file is saved in the context directory defined by the ResourceFinder.
Currently, a session is defined as 5 seconds session, but the sequencer (#5) will define it.

Exported data are in the following format:

• Keypoints is a Nx1 struct (N = number of sessions), containing raw data.
  The struct contains 14 fields. Each field has a name corresponding to a keypoint and for each session contains a matrix nx3 (n = time sample) in the following format:

[x1, y1, z1; 
 x2, y2, z2; 
... 
 xn, yn, zn]

• Time_samples is a nx1 vector containing the time samples at which the keypoints are received
• Metric name (for example ROM_0) is a Nx1 struct, containing tstart and tend, which indicate the start and the end of a single session, and the following information from the motion repertoire (which might change depending on the metric):

1. • ref_joint: reference joint for the considered metric
2. • ref_direction: reference direction for the considered metric
3. • ref_plane: plane on which the metric has to be evaluated
4. • max: max value for the considered metric
5. • min: min value for the considered metric

[pattacini]

Very nicely done @vvasco 🏅