title: Sorting group columns in ag-grid
body: <p>I am grouping (and aggregating) on a column.  Using the example on the ag-grid site, let's say it's Country.   I am using these options:</p>
  
  <pre><code>groupUseEntireRow: true,
  groupHideGroupColumns: true
  </code></pre>
  
  <p>and when I define the Country column in the columnDefs I add:  rowGroupIndex: 0</p>
  
  <p>But when the grid loads, the Country groupings do not show in alphabetical order by default. How can I get them to sort?  I didn't see anything in the documentation that explains this.</p>
  
  <p>Note that I do NOT need to allow the user to sort Country later, I just want to order by Country when the grid loads.</p>