title: ExtJS 4 select multiple CheckColumn checkboxes with checkbox header
body: <p>I have a column of <code>checkcolumn</code> type to enable toggling boolean values. I'd like to be able to toggle all rows for that value at once. Ideally, I'd be able to add a checkbox to the <code>checkcolumn</code> header and listen for changes. Is that possible?</p>
  
  <p>I'd like to note that I am not looking for a checkboxmodel to select rows.</p>