Updated PR for NSOutlineView/NSTreeController due to refactor

[gcasa]

Subject summarizes. This PR is meant to implement NSTreeController and NSOutlineView integration. I made a new branch since NSOutlineView was heavily modified in the PR addressing NSTableRowView here.

[gcasa]

@fredkiefer This is not yet ready for review. I will convert it when it is. Thanks.

[gcasa]

Interesting indeed...

Found 20 methods on '_NSControllerTreeProxy'
	'_NSControllerTreeProxy' has method named 'count' of encoding 'Q16@0:8'
	'_NSControllerTreeProxy' has method named 'indexPath' of encoding '@16@0:8'
	'_NSControllerTreeProxy' has method named 'parentNode' of encoding '@16@0:8'
	'_NSControllerTreeProxy' has method named '_invokeSelector:withArguments:onKeyPath:ofObjectAtIndexPath:' of encoding 'v48@0:8:16@24@32@40'
	'_NSControllerTreeProxy' has method named '_setValue:forKeyPath:ofObjectAtIndexPath:' of encoding 'v40@0:8@16@24@32'
	'_NSControllerTreeProxy' has method named '_validateValue:forKeyPath:ofObjectAtIndexPath:error:' of encoding 'c48@0:8^@16@24@32^@40'
	'_NSControllerTreeProxy' has method named '_valueForKeyPath:ofObjectAtIndexPath:' of encoding '@32@0:8@16@24'
	'_NSControllerTreeProxy' has method named 'childNodes' of encoding '@16@0:8'
	'_NSControllerTreeProxy' has method named 'countForIndexPath:' of encoding 'Q24@0:8@16'
	'_NSControllerTreeProxy' has method named 'countOfChildNodes' of encoding 'Q16@0:8'
	'_NSControllerTreeProxy' has method named 'descendantNodeAtIndexPath:' of encoding '@24@0:8@16'
	'_NSControllerTreeProxy' has method named 'initWithController:' of encoding '@24@0:8@16'
	'_NSControllerTreeProxy' has method named 'isExpandableAtArrangedObjectIndexPath:' of encoding 'c24@0:8@16'
	'_NSControllerTreeProxy' has method named 'isLeaf' of encoding 'c16@0:8'
	'_NSControllerTreeProxy' has method named 'mutableChildNodes' of encoding '@16@0:8'
	'_NSControllerTreeProxy' has method named 'nodeAtIndexPath:' of encoding '@24@0:8@16'
	'_NSControllerTreeProxy' has method named 'objectAtIndexPath:' of encoding '@24@0:8@16'
	'_NSControllerTreeProxy' has method named 'objectInChildNodesAtIndex:' of encoding '@24@0:8Q16'
	'_NSControllerTreeProxy' has method named 'representedObject' of encoding '@16@0:8'
	'_NSControllerTreeProxy' has method named 'sortWithSortDescriptors:recursively:' of encoding 'v28@0:8@16c24'

I am introducing an equivalent class GSControllerTreeProxy to fill this role, it will be a subclass of NSTreeNode, just as _NSTreeControllerProxy is. Apparently, NSTreeController is not meant to handle an NSArray of objects. This is apparent from the documentation as - (NSTreeNode *) arrangedObjects is defined as such.

I will need to work out the nuances of how this handles various bindings.

[gcasa]

The test for this is here... https://github.com/gcasa/NSTreeController_test

[gcasa]

Here is NSOutlineView using a dataSource...

And here it is using a binding...

This demonstrates that the new code does not affect outline view functionality in other applications.

[gcasa]

I am marking this as ready for review and proceeding to optimize and clean up the code in preparation for merge.

[gcasa]

Of course, Gorm works as well...

[gcasa]

@fredkiefer These changes are mainly about the binding between NSTreeController and NSOutlineView. More changes might be forthcoming, but I will do some of the other methods as separate PR. Please take a moment to review.