Big update, saved .pkl informations, track handling

Change the structure to better handle tracks. Can now save/load the graph, groups and suspects informations. All saved in .pkl file. Added edit operation directly on track (affects several frames at once) Added option to interpolate a label Grid show/hide options in display Suspect options: can zoom, remove or select from shortcuts Tracks: same color as label. Update only by clicking on button, otherwise update is done in local variable in the code (not visible)