Keep track of when the user has modified the tartan. This is all states except

• we have just started up
• we have just uploaded a tartan (not exported one as jpeg)
• we have just downloaded a tartan from Commons

If we're modified, the window title gets a "*" at the end.

If you try to close the window when we're modified, you get an "Are you sure?" message.

Much of this code already exists, but was commented out or disabled when we went properly MVC.