title: QTreeWidget : disable a line but not the subtree
body: <p>I use a QTreeWidget that shows a file listing so that a user can copy files to a directory.
  I want to disallow the user to copy the files to the same directory.
  Thus, I want to disable just one line in my QTreeWidget so that it is not selectable. I tried to use the <code>setDisable(bool)</code> method of the QTreeWidgetItem object but the problem is it disables the whole subtree.</p>
  
  <p>How to get just one line disabled in a QTreeWidget ?</p>