Initial dockerization

* Dockerfile creation for both web and DB servers
* Modified a few paths to accept optional ENV vars so that the app will function inside of a Docker container. Non-Docker operation is not affected.


@craig8196 - I'd appreciate your review on this commit.  Of interest are the changes to the working dir location on imports.  They were a hard-coded path, but to function inside a Docker container I had to make their location configurable.  I did that via ENV vars, which the Docker container sets for itself.  In the absence of those variables, things work as they did before.  I do have documentation forthcoming on Docker, so how to use it will become clear as well, if you're interested in doing so.

Lastly, I updated a few of the entires in requirements.py.  I capture the postgres driver under #optional, and the git python package appeared to be called `gitpython`.