Improve 3d figure legend #66
Description
The legend in all 3d figures created with plotly (output from plot_3d & pfss_3d) should be updated to correctly include the markers='number' # or 'letters' option (i.e., having numbers/letters on the markers) and provide an arrow for the "reference" entry. Unfortunately, as this plotting option is hacked into plotly manually, this would (at the moment) also need some amount of manual work.
