title: Correct way to implement multi-folder menus
body: <p>I'm a bit stuck trying to implement a multi-level folder grouping. The top level folder lists a few line items, each of which plays a track. What I'm trying to accomplish is have one of these items be a folder which leads to another playlist (since this is a music add-on, they're all 'playlists').</p>
  
  <p>Here's a snippet of what I'm working with that works for the top level. What I cannot figure out is how to utilize the <code>isFolder=True</code> flag appropriately, spanning multiple folder levels. </p>
  
  <pre><code>total_items = 0
  for key, _x in self.bd_config.items('streams'):
      total_items += 1
  
      url = self._get_stream(key)
  
      # Generate a list item for Kodi
      li = xbmcgui.ListItem(label="Bassdrive @ %s" % key, thumbnailImage="%s" % os.path.join(self.bd_ppath,
                                                                                             'icon.png'))
  
      # Set our stream quality, per Bassdrives website
      li.setProperty("mimetype", "audio/aac")
      if key == '128k':
          li.setProperty("mimetype", "audio/mpeg")
  
      # Set player info
      li.setInfo(type="Music", infoLabels={"Genre": "Drum &amp; Bass",
                                           "Comment": "World Wide Drum &amp; Bass",
                                           "Size": int(key[:-1]) * 1024})
      li.setProperty("IsPlayable", "true")
      xbmcplugin.addDirectoryItem(handle=self.bd_handle, url=url, listitem=li, isFolder=False,
                                  totalItems=total_items)
  
  print total_items
  
  # tell XMBC there are no more items to list
  xbmcplugin.endOfDirectory(self.bd_handle, succeeded=True)
  </code></pre>