Implement orbital rotations

[jagot]

To speed up convergence, for systems where infinitesimal rotations do not change the eigenvalues (such as atoms), explicit rotations of orbitals of the same symmetry are helpful, since they define a unique solution.

Discussed in section 4 of

• Fischer, C. F. (1986). Self-Consistent-Field (SCF) and
  Multiconfiguration (MC) Hartree-Fock (HF) Methods in Atomic
  Calculations: Numerical Integration Approaches. Computer Physics
  Reports, 3(5),
  274–325. http://dx.doi.org/10.1016/0167-7977(86)90001-8