Fixed: shouldSelectRow was called with selectionIndexesForProposedSelection

Previously the method shouldSelectRow was called even it's the method selectionIndexesForProposedSelection was implemented by the delegate. Now it works as in Cocoa.
The method selectionIndexesForProposedSelection is called when it has to be called, like in Cocoa.
This PR adds new methods to check and call the delegate/datasource methods more easily

Test app in Tests/Manual/TableTest/DelegateSelectionTest/

AppKit/CPTableHeaderView.j

@@ -382,7 +382,7 @@ var _CPTableColumnHeaderViewStringValueKey = @"_CPTableColumnHeaderViewStringVal
         _mouseDownLocation = currentLocation;
         _activeColumn = columnIndex;
 
-        [_tableView _sendDelegateDidMouseDownInHeader:columnIndex];
+        [_tableView _mouseDownInHeaderOfTableColumn:columnIndex];
 
         if (shouldResize)
             [self startResizingTableColumn:columnIndex at:currentLocation];