Minimal postgresql support in dbUtils

[jtniehof]

This is a start on #14 but by no means complete. It's an attempt to get us towards working PostgreSQL without having everything perfectly in order. In particular, it still uses the magic environment variables rather than completely generalizing the database URL.

This PR gets as far as being able to create the tables in a PostgreSQL database and start addFromConfig. Unfortunately there are some aspects of the behavior in dbUtils that are relying on sqlite, in particular weak type checking. I can do some work on that later but wanted to get this up for merge first so we don't duplicate effort. This should not affect current working sqlite setups.

PR Checklist

• [X] Pull request has descriptive title
• [X] Pull request gives overview of changes
• [X] New code has inline comments where necessary
• [X] Any new modules, functions or classes have docstrings consistent with dbprocessing style
• [X] (N/A) Major new functionality has appropriate Sphinx documentation
• [X] (N/A) Added an entry to release notes if fixing a major bug or providing a major new feature
• [X] (N/A) New features and bug fixes should have unit tests
• [X] Relevant issues are linked in the description (use Closes # if this PR closes the issue, or some other reference, such as See # if it is related in some other way)

There's no Sphinx documentation or release notes yet since the functionality isn't completed. Similarly for testing--there's a skeleton of a functional, but ultimately the unit tests will have to be reworked to support all of this.

[jtniehof]

This is what I get for being lazy. Fixed.