Adding a new refinement criterion (19) to refine on metal mass instead of some minimum metallicity. This strategy favors dense metal-enriched gas and will not aggressively refine underdense enriched regions.
Refinement criteria is similar to baryon mass refinement, but with the minimum mass multiplied by MetallicityForRefinement * Zsolar, where Zsolar = 0.0204. Default = 1.
Also, fixed a bug in the hydro_rk MHD color species, where density was renormalized twice.
For this comment: "...but with the minimum mass multiplied by MetallicityForRefinement * Zsolar, where Zsolar = 0.0204." Shouldn't this be updated to be more consistent/accurate -- following the discussion that was had by @Britton Smith as part of updates to Grackle?