title: Adding a filter header row to ExtJS GridPanel
body: <p>I know that it's possible to add a filter row UNDER the column title because I've seen it done with Coolite. But since I'm a total newbie with Sencha (ExtJS), I have trouble finding how to do it with the ExtJS.grid.GridPanel directly in the script. Would you point me in the right direction with some samples please ?</p>
  
  <p>If possible, I would like to do so without plugins, but if there's one out there doing great and easy to use, I could change my mind.</p>
  
  <p>Thanks ! </p>