Pure db configuration function from configure-db

configure-db-from-environment was made so that it would only grab connection information from the system properties. However, it is very useful to be able to directly provide the connection information from another source (for example the system environment in heroku). 

The configure-db-from-environment still exists and should work the same, but now has a pure function backing it that takes strings representing the connection information instead of a string indicating the property to access.