title: Determine whether Selector.SelectionChanged event was initiated by a user
body: <p>Is it possible to determine whether a <code>Selector.SelectionChanged</code> event was initiated by the user or programmatically? </p>
  
  <p>I.e. I need something like a boolean <code>"IsUserInitiated"</code> property that is true only if the <code>SelectionChanged</code> event was raised because the user changed the selection using mouse or keyboard.</p>