title: On Grid with grouping feature, change the sorting order in the grouped column
body: <p>As an example, suppose that a grid exists with the following columns: Name, Age, Pet.</p>
  
  <p>Also suppose the only possible pets are from the set (Dog, Cat, Fish).</p>
  
  <p>I have applied the grouping feature with <code>groupField: 'Pet'</code>. By default, the grid is rendered with the rows grouped by pets in the ascending order of possible pets.</p>
  
  <p>Something like:</p>
  
  <pre><code>Pet: Cat (30)
  ----------------
  [30 Cat Rows]
  
  Pet: Dog (10)
  ----------------
  [10 Cat Rows]
  
  Pet: Fish (10)
  ----------------
  [10 Cat Rows]
  </code></pre>
  
  <p>I want to control the sorting order of the grouped column too, so the order of the groups can be descending too:</p>
  
  <pre><code>Pet: Fish (10)
  ----------------
  [10 Cat Rows]
  
  Pet: Dog (10)
  ----------------
  [10 Cat Rows]
  
  Pet: Cat (30)
  ----------------
  [30 Cat Rows]
  </code></pre>
  
  <p>The above should be supported for any column (on which grouping is possible) in the grid.</p>
  
  <p>Is there a way to achieve this?</p>