moved settings activation code to window controller. Vastly improved comments.
Better emptiness behavior.
Now you get one big button telling you to add. If you launch prefs without any shells, you immediately start by adding one.
simplified hiding/showing by extending NSDictionary.
More NSDictionary extension, less explicitly stating every little thing in the window controller.
Pushed the giant overlay button to the back (duh, right?) and removed some pointless logging.
Defined table data source in code rather than in XIB. Fixed table row height.