Add HGP2018 solution models

[bobmyhill]

The HGP2018 dataset currently contains only the endmembers and the melt model (#454). The following models still need to be added (from tc-ig50NCKFMASHTOCr.txt):

• Aqueous fluid: KNCFMASTOCr
• ternary plagioclase: Ibar1 ASF
• ternary plagioclase: Cbar1 ASF
• olivine: CFMS
• ternary ksp (Cbar1 ASF): NCKAS
• muscovite: NCKFMASHO
• biotite: KFMASHTO
• garnet: CFMASTOCr
• epidote: CFASHO
• Cordierite: FMASH
• Orthopyroxene: NCFMASTOCr
• Clinopyroxene: KNCFMASTOCr
• Spinel: FMATOCr
• clinoamphibole: NCKFMASHTO
• Ilmenite: FTO

There are other models in the metapelite set

• Garnet: CFMMnASO
• Granitic 'metapelite' melt: NCKFMASH
• ternary ksp (Cbar1 ASF): NCKAS
• ternary plagioclase (Cbar1 ASF): NCKAS
• margarite: CNKFMASHO
• biotite: KFMMnASHTO
• orthopyroxene: CFMMnASO
• sapphirine: FMASO
• Cordierite: MnFMASH
• staurolite: FMMnASHTO
• chlorite: FMMnASHO
• Chloritoid: FMMnASHO
• Ilmenite: FMMnTO
• Magnetite: FTO (subsolidus only!)

The metabasite set doesn't seem to have any models that are unique to that system.

[bobmyhill]

Addressed by #594 and #595.