Fix Z scaling for Freedman et al. opacity tables

Freedman opacities assume the Lodders 2003 solar composition. The tables are at [M/H]=-0.3, 0, +0.3, +0.7, +1.0, +1.5, and +1.7. kap/preprocessor scales these w.r.t. Z=0.02. Lodders 2003 Zsol = 0.0133 != 0.02 so the scaling done in kap/preprocessor needs to be fixed.

Unfortunately, they do not say in the paper how exactly they scale He with "M" and/or H so we can't be sure what Z values these [M/H] correspond to.

Start in kap/preprocessor and trace how the Freedman opacity tables are scaled relative to Z=0.02. Compare that logic with the Lodders 2003 solar composition value Z=0.0133 and the [M/H] table values. Resolve how hydrogen and helium are intended to vary before changing the scaling, then validate the resulting metallicity mapping.

Written by the indexing model from the issue text.