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Initial commit of the new Architectural classes needed to implement the login system.
Created the MasterNavigator class. This is a singleton class (only one instance of it exists globally) that contains a Navigator object. (The navigator object is responsible for handling which webform gets displayed, the URL for the form, etc. The navigator loads and executes classes which implement the View interface, calls the class' .enter() method, and then proceeds. The beauty of this is that any Spring Security Authorization (user level) checking can be done at the .enter() method, and an Access Denied can be thrown securely.)
Got the Navigator to work (sorta). It now loads the login view. Had to re-subclass MainShellView and LoginView from UI to Panel. UI seems to be pretty greedy in it's importance within the application.

Need to add a button-click listener to the login form, and try and get that listener to talk to the master navigator to navigate to the MainShellView.
More fiddling to get the button click handler working. When I got bored of that, I tried to center align the login form on the page.
Fixed the NullPointerException on the login page. Turns out that the singleton I made initially never had a way to change it's contained Navigator object to anything but null. Woops.

Fixed now. You can run the application, click login, and it changes the view to the main screen.

I've been reading about Spring Security integration with Vaadin. Because vaadin is so huge, it's not a trivial thing to bolt on spring security. I don't have enough of an understanding of the Eclipse build system (and Geronimo) to know where to put various config files and classes.