Porosity not printed to GAIA results file

As described in post #42908, the porosity for layers *XKV is seemingly available in the graphic printout options in the DICO, but does not actually get printed out at runtime. There doesn't seem to be any relevant code to do the writeout.

Porosity appears to be necessary for restarting computation, if mass is not given. This is something I would like to use to resume computation with some intermediate adjustments (merging two files, but that's a separate topic!), as it seems simpler than calculating the mass myself.