On first login, show a message indicating that you are already logged in

[paulproteus]

Per feedback from @cwebber, we could do something to clearly indicate to MediaGoblin users via the Sandstorm demo (and the package generally) that the user has already been logged in.

One option is to add something special to the template on first login indicating, "This is Sandstorm! You're logged in! Everything's great!"

The way this works in normal, CLI-admin mediagoblin is that you create an admin account via CLI and then you log in, so you already know that you're logged in as an admin.

[paulproteus]

Upon further discussion, we decided we can possibly make this something upstream does generally. I'll see if I can work on a patch for upstream.