Consider making getting started easier

[alankley]

Consider caching user preferences and skipping login and Group selection on startup.

Once a user logs in, we can keep them "logged in" for a period of time or until they "logout". On the login screen, we can have a checkbox giving them the choice of "keep me logged in". If checked, the next time they launch Trovami it skips the login screen.

We can also always use the last group selected. Group management/selection would only display if they choose to edit groups