Changed the icon cell renderer to no longer use the property change notification.  Also fixed some bugs that cause it to not display the selected backgrounds.  Added additional interfaces to expose members and properties on a TreeNode object.
Removed the NullTreeObserver the the TreeObserver completely.  This is not the right way to go.
Added the WeakLocator so objects don't have to pass around factory objects to create this basic object.
Updated
Added an event aggregation feature to the infrastructure.