refactor: Species AtomTypes

[trisyoungs]

This PR is the first significant step towards removing the old Dissolve and CoreData classes, removing the storage of AtomTypes in CoreData. It breaks a couple of things related to the AddForcefieldDialog but the justification for doing so is that this is likely to be completely rewritten (most likely in a more Node-y form) for Dissolve2.

Blockers

(In order to fully remove AtomTypes from CoreData)

• PotentialSet stores AtomType pointers and needs to serialise them, so must be converted to use a DoubleKeyedMap of resolvables
• AtomTypeVectorKeyword stores AtomType pointers and needs to serialise them, however is only used in a single place in the old NeutronSQModule.
• EPSRModule::readPCof converts names into AtomTypes using CoreData.
• ForcefieldSortFilterModel::filterAcceptsRow uses a temporary Dissolve and CoreData to assign atom types and check for forcefield validity.
• DissolveModel exposes AtomTypes through its AtomTypeModel, but this is no longer relevant as they are local to Species (same for master terms).
• AddForcefieldDialogModel uses temporary Dissolve and CoreData extensively, including but not limited to AtomTypes. Since AtomType and master term data are to be local to a Species, much of the existing checking is irrelevant.
• EPSRModuleTest accesses the test object's CoreData to get the number of atom types which (currently) is both unnecessary and incorrect!
• AtomTypeModel (used in lots of places) uses CoreData::atomTypes_ to check for unique naming when renaming an atom type.