updated gstlal-inspiral/bin/gstlal_inspiral_mass_model with "salpeter_primary"
Added changes to gstlal-inspiral/bin/gstlal_inspiral_mass_model to account for the mass model proposed for O4, now named in the code as "salpeter_primary" found here. This mass model has component mass 1 ~ 600 MSun, m1 follows a power law of -2.35 (=Salpeter), and m2 is constant.