title: Automatically hide "empty" columns in ExtJS grid Panel
body: <p>Is there a plugin for the ExtJS Grid that automatically hides "empty" columns?</p>
  
  <p>A column should be deemed "empty" if the value of the mapped field for all Records in the underlying store matches a given "emptiness" criteria (a given value or, better, a function).</p>
  
  <p>Run-time add/remove/update operations on the underlying store should hide/un-hide columns accordingly.</p>
  
  <p>Thanks!</p>