Clarify orbital properties for open-shell systems

[ghutchis]

Currently, the specification does not clarify how to handle orbital energies, occupations or symmetries for open shell systems.

For coefficients, moCoefficients splits into alphaCoefficients and betaCoefficients but this makes the other lists ambiguous.

[ghutchis]

My suggestion is that for open shell systems, orbital energies, occupations and symmetries become lists of lists (alpha, beta).

Right now, if I look in quantumio I don't see any code that uses:

• gaussian->moEnergy()
• gaussian->moOccupancy() etc.

So all of this is new syntax - it does not yet exist in the wild.

Alternately, the energies, etc. could use the same scheme - orbitals:energies gets split into orbitals:alphaEnergies and orbitals:betaEnergies, etc.

That second option is probably easier to code, since the GaussianSet::setMolecularOrbitalEnergy takes alpha / beta types.