title: ExtJs 4.1 TreeGrid Filter through Column Headers
body: <p>I've been searching around and looking into the documentation, but I'm not sure how to activate filtering via the column drop down the way you have it in normal grid panels. </p>
  
  <p>I've tried to implement the <code>ux.Grid.FilterFeatures</code> but when I apply it to the tree panel, my panel doesn't render properly (all blue panel). I thought it might have something to do with its deferred layout, but when I do a <code>treegrid.hide()</code>/<code>treegrid.show()</code>/<code>treegrid.doLayout()</code>, it doesn't make a difference. </p>
  
  <p>Has anyone gotten the filter feature working with the treepanel? Or has anyone got any suggestions on how to rectify this problem?</p>