have code error out if metallicities exceed tabulated fsps metallcities

[dnarayanan]

only relevant for idealized simulations, quantities (e.g.):

disk_stars_metals = 11 # in fsps metallicity units

or alternatively, have user put in metallicity in units of solar, and have the code figure out which tabulated value this corresponds to, to minimize issues like this.

[dnarayanan]

at least one point that throws an error is lines like:

 else:
        dmet = [fsps_metals[cfg.par.disk_stars_metals]]*len(diskmasses)
        ```
        
        in `analytics.py`