Provide command line variables for initializing an admin user.

Provide command line variables for initializing an admin user. Previously to get admin access on a fresh install I had to create a user in the web interface (to make sure the password hash/salt is properly setup) then manually change the role in the database to 'admin' using a postgresql client. This was a pain in the ass, and I think there really needs to be an easy way to create the admin user on the initial deployment. This solution fixes this, and adds documentation to the README file on how to use those variables.