SQLAlchemy integration

The notion is that settings.py is the defaults, and settings.cfg is able to override as needed (note the file that includes them, which first pulls from geordi.settings, and then from settings.cfg ignoring errors -- i.e., if settings.cfg doesn't exist it won't break the whole thing. I'm not sure how well that actually works in practice. Presumably at least OAUTH_REDIRECT_URI should be brought into settings.py (so that it only needs overriding for public-facing sites), and the new sqlalchemy default config can also be there.