Support Monorail API Login

[spiegela]

The current implementation requires the user to authenticate externally. The client should support local username and password authentication.

[spiegela]

I think the best way to add this will be to add a Login() method to the wrapping struct. This way the auth credentials can be injected into the underlying swagger-generated methods.

This can also add the ability to re-authenticate the client during auth timeouts.