Additional Preset: Geothermal Brine

[rkingsbury]

Add an additional preset in the form of a .yaml file that represents geothermal brine. The difficulty will be deciding what "representative" means, and it will be important to be clear in the docstring that the composition of such brines varies widely. Table 12 of Stringfellow et al. and the references it cites would be a good starting point.

Depending on HOW widely composition varies, there could be multiple presets corresponding to, e.g. high and low salinity geothermal brine, or brine from specific aquifers