Fix issues with Gasteiger atom typing
Riley and Doug noticed that the gasteiger typing didn't work in the
presence of virtual atoms. This was a known issue, but this commit should
fix that.
Also add unit tests for Gasteiger typing on the cannonical amino acids and
nucleic acids. This involves annotating the database params files with
bond type and formal charge information, as well as putting in code to deal
with connection points in the gasteiger typing.
All the default loaded, non-patched full atom residue types should be cleanly
and accurately(?) typed.
No integration or unit test changes expected.