title: GWT how to add a custom cell to celltable/datagrid
body: <p>I have rendered a custom cell which combines an image and text.
  It looks like this: </p>
  
  <pre><code>   class ImageTextCell extends AbstractCell&lt;String&gt; 
  </code></pre>
  
  <p>My question is how to add this cell into celltable/datagrid.
  I have tired this.</p>
  
  <pre><code>  Column&lt;Message, String&gt; iconColumn = new Column&lt;Message, String&gt;(new ImageTextCell())
              {
          @Override
          public String getValue(Message versionStatus) {
  
              return ? // I dont know what to type here. How to return the ImageTextCell object           }
      };
  </code></pre>