Refactoring workflow

And by that, I mean I'm refactoring how commands are routed. Should
be fun...
Continuing with the refactor
Finished user creation.

Server saves new users to the database and returns an error if
that user is already present.
Almost finished CRUD operation stubs

Still need to finish "Update", but otherwise, the stubs work. Also have to
parameterize the "Read" functionality so it doesn't just search on usernames,
but also for ID's any names. We'll figure that out later...
Unit testing, ahoy!
Finished Create and Delete unit tests

And fixed a bug in the user-handler that didn't break the "delete" case
properly. Now the server doesn't send back an error message.