Change how multiple second-level groupings are treated #10
Description
Currently, Mist assumes the the JSON file has a list of all phases as a separate entry from the properties associated with each phase. Strictly speaking, that is redundant and we should be able to pull that information from the keys. The composition is in a similar boat. In that case we might still want to be able to list what the "base element" is. If we have a specific composition given, then we might be able to determine that algorithmically, but for e.g. a general AlCu alloy it'd be useful to specify that we consider it "an aluminum alloy" and not "a copper alloy" for some workflows.