Add lightcurve plot with excess indication

• Add timewise_sup.plot.diagnostics:plot_lightcurve_regions: creates a lightcurve plot with separate panels for each band and indicates the excesses and the baseline datapoints.
• DatabaseConnector.get_excess_mjds now takes an additinal argument which.
  • 'max': the times of the brightest excess are returned (behavior as before)
  • 'all': the times of all excess regions are returned, dimension is 2!