[RM-8104] Halpha global flux estimation, add NII

Created on 2023-05-31 10:30:10 by Didier Vibert. % Done: 100

the Halpha SNR and flux (lfHa, snrHa) output in the dataset "model_parameters" compute the direct-integration flux for Ha alone (where as for OII it computes the flux of the double).

add NII doublet to the Ha complex.

compute also the Gaussian fit flux (just compute the flux sum of the individual lines)

(note: no change on the fluxes in the fitted_lines output dataset)