Command to create initial database user

When setting up a new instance of Comrad, there isn't an easy way to create an initial admin user. Let's set up a command that can be run with `npm run` and create that initial user.

Once that's in place, update the "Seed the Database" section of https://github.com/codefordenver/Comrad/blob/development/docs/production_server_setup.md with instructions to use this new utility.