NWChem: parse aonames

Use the section about shells to generate ```aonames```. 

This is still unfinished, and needs the following prior to merge:

* Higher shells and larger basis set examples. Ideally have f- and g-orbitals, in addition to d-orbitals.
* Unittest to make sure everything works as expected.
* Verify the order of cartesian/spherical labels, especially for d-orbitals and higher.