title: Signal a QTreeWidgetItem toggled checkbox
body: <p><a href="https://stackoverflow.com/questions/23477625/how-do-i-check-if-a-checkbox-is-checked-or-unchecked-in-qtreewidget?rq=1">How do I check if a checkbox is checked or unchecked? (In QTreeWidget)</a> shows how to get the status of the checkbox on a qtreewidget item.  Using that method, with a signal for itemClicked in the Tree, I can query if the selected item is checked or not.  However, I then need to keep track of this item to see if it was previously checked or not.  </p>
  
  <p>Is there a method for knowing that a QTreeWidgetItem, which may be at different levels from the parent items, has a toggled checkbox, without making a subclass for it?  </p>
  
  <p>As a note, is there a specific reason the toggled method is not attached to the QTreeWidgetItem in QT?</p>