title: Checking 'Use Count' for library items with JSFL
body: <p>I've done a bit of research and from what I've read there seems to be no equivalent in JSFL for the "Select unused items" in the Flash IDE.</p>
  
  <p>Does anyone know of a property to at least be able to check if the item is used by cycling through the whole library? something like item.useCount...</p>
  
  <p>I'm checking the adobe documentation and I can't find anything...</p>