Streamline binding implementation....

[gcasa]

For NSBrowser and NSTreeController/NSOutlineView, and other classes bindings have been implemented. However, the implementation is not as clean as we want. The functionality works and passes testing, but is not as elegant as it should be. Testing has indicated that there is an "adapter" pattern that is being used. This might clean up the implementation.

The acceptance criteria of this is:

1. Implement GSBindingsAdapter class
2. Clean up existing implementation of bindings in NSOutlineView, NSTreeController, and NSBrowser

GC