title: Creating custom ActionCell in CellTable Column
body: <p>I want one of my table columns to have a deleteButton.</p>
  
  <pre><code>ActionCell&lt;Entrata&gt; deleteCell = new ActionCell&lt;Entrata&gt;("x",new Delegate&lt;Entrata&gt;() {
              @Override
              public void execute(Entrata object) {
                  // rpc stuff.... 
              }
          });
  </code></pre>
  
  <p>Ok but this line generates an error: </p>
  
  <pre><code>Column&lt;Entrata,Entrata&gt; deleteColumn = new Column&lt;Entrata, Entrata&gt;(deleteCell);
  </code></pre>
  
  <p>"Cannot instantiate the type Column"</p>
  
  <p>What do you think?</p>