In progress.  adding hooks to more FSPS functions, moving some parameters from csp to ssp

evtype, redgb, masscut, and fcstar are all (undocumented) parameters that affect the SSP generation, so I moved them to ssp_params, and updated documentation.

Also, the index order of ssp_spec_zz, ssp_lbol_zz, and ssp_mass_zz changed in FSPS to speed up some operations, so I've updated the relevant lines in fsps.f90.

Finally, I am adding bindings to the smoothspec routine and the new ztinterp routine, as well as exposing ssp_spec_zz to the StellarPopulation object.