Robust electronic structure visualization

[tjduigna]

The "add_molecular_orbitals" and associated functionality seems to more or less work for the quantum codes that have the required parsers (molcas, gaussian, nwchem?, adf used to?). However, due to internal differences in the order of operations and conventions for dealing with segmented/contracted/cartesian/spherical/cubic functions, it is not easy to guarantee that evaluation of molecular orbitals on a grid by "quantum-code agnostic" routines gives necessarily idential results to the quantum codes themselves.

This issue serves to track progress towards developing what essentially amounts to implementing computation of the overlap matrix and validating with a given set of molecular orbital coefficients. This procedure should be done on the fly "per universe" and throw a warning if something doesn't look quite right. This type of check will probably never be computed for STOs.