title: Is it possible to set a property on QTreeView item
body: <p>QSS allows styling <code>QTreeView</code> and has a set of predefined child elements, e.g. <code>QTreeView::item</code>.
  I would like to add finer model-driven granularity to it using property selector (<code>QTreeView::item[myproperty=myvalue]</code>). This way I could have data-driven display and at the same time it would be customizible via QSS.</p>
  
  <p>Is there a way I could access the item of <code>QTreeView</code> (note, not the <code>QTreeWidget</code>), so that I could set a property on it based on the data returned from the model?</p>
  
  <p>Are there any other ways of driving which style to apply to a given item from the model (other than returning font, color etc)?</p>