title: ExtJs GroupingView prevent sorting of the group title
body: <p>How to prevent sorting of the group title in GroupingView. By default group titles are sorted 'ASC'. I have a situation where "Adhoc Reports" group should order last in the GroupingView.</p>
  
  <p>I need the group title to be in the following order</p>
  
  <p>groupName: 'Federal Reports'
  groupName: 'State Reports'
  groupName: 'Ad Hoc Reports'</p>
  
  <p>This is how these are grouped in the JSON. </p>