Some rearranging in MEH.
separating out form_sigma in DistFCI
MEH with distributed FCI. Compiles, but crashes while building the GammaTree.
MEH_DistCAS works on one node but it fails for two nodes and is very very slow.
MEH works with DistFCI. It could still stand to be optimized, but at least it works.
Merge branch 'master' into dist-meh

# By Toru Shiozaki
# Via Toru Shiozaki
* master:
  started to implement +1 sector. (b^+b^+ ba) implemented. Next (b^+a^+aa) and (b^+a)
  got it - everything is consistent by now. Next +/-1 and +/-2 sectors
  cleanup. mystery still unsolved.
  bug fix. Diagonal part seems correct, but there is one counterintuitive step that I need to verify.
  minor
  assert statements using reconstruction of the Fock operator using Kramers adapted orbitals
  bug fixes. Still broken
  ZHarrison runs and converges but not sure if the calculation is correct.
  Deleted useless codes. Links in place.
  AB1 and AB2 in ZHarrison
  BB is straightforward given AA
  HZ AA task is now template and should work with ZHarrison (at least it runs through)
  Stab at the diagonal part
  ZHarrison is now an independent class.