Rework processing pipeline

[MarcBresson]

 - initialise an empty array to store all the data

- For each video:
    - parse the labels.json file
    - parse the fps/yolov7.json file

    - for every data_augmentation:
        - for each frame:
             - initialise a dictionnary for every unique skeleton as they will require separate rolling windows (only if multiple people on the frame)
             - if the offender skeleton is tracked
                 - add it to the rolling window (or create the rolling window is the skeleton id didn't exist)
                 - process it (velocity, velocity centre, angles)
                 - store it

- save the file