Add ability to output initial Hartree-Fock state

[cferenba]

This PR adds logic to hamgen.py to output the initial Hartree-Fock state. A few notes:

• Currently the output format is .npy, to match what's done in the time-evolution code. It shouldn't be difficult to add other formats if needed.
• For now I'm assuming that all active electrons are in the lowest active orbitals. A better solution would be to use the electron location pyscf_scf.mo_occ, except that information is currently lost in the transition from ham1 to ham2.
• Let me know if you have better names to suggest for any of the variables or functions. In particular I notice that the term state is now overloaded, being used for both the configuration information and the initial state vector.