Add non-required authentication (including user account management) to the application

For more advanced features, we require registered, authenticated users. 
To achieve this, please add authentication and user management to this application. 
This was previously done in delphi-hub/delphi-management#11 and delphi-hub/delphi-management#12. 

We really have to think hard here if it is wise to have a single user pool or a separate user management.