settings version 2

[ExpHP]

rsp2 no longer introduces breaking changes for existing settings.yaml files (aside from the outright removal of a feature), but a version field will be added to allow breaking changes to be opted into. (all files without a version default to version: 1)

A running list of breaking changes I want to occur when version: 2 settings are introduced:

• Remove deprecated items:
  • Deprecated names of potentials.
  • The rsp2 eigensolver. (now dense and sparse)
  • Lammps things that were moved under the lammps: heading.
• Rename kc-z-new to kc-z, replacing the old (deprecated) kc-z.

• threading:
    potential: true