TreeView drag and drop into item behaviour

General JUCE discussion
1

When I drag an item of a TreeView and I drag it onto another item it always shows drag feedback that says I can drag the item onto the other item. But if the other item is actually a leaf item and it does not accept sub items the feedback needs to show that. This is determined by the InsertPoint subclass, which should use the TreeViewItem virtual method mightContainSubItems to determin that. I made this change that corrected that behaviour:

                    // Check if we're trying to drag into an empty group item..
                    if (oldY > itemPos.getY() + itemPos.getHeight() / 4
                         && oldY < itemPos.getBottom() - itemPos.getHeight() / 4
>>>						 && item->mightContainSubItems())
                    {