title: how to add a disclosure panel to a cellTable column in GWT
body: <p>I have a cellTable with 5-6 columns. I want to put a plus icon in each row on clicking of which will display the details maybe in a disclosure panel. I have been looking around for a while now and I cannot find any information on how to achieve this. Could someone point me in the right direction?</p>
  
  <p>i suspect  i probably have to add a cellTree to the column? how do i go about this? 
  Thank you for your response in advance.</p>