title: GWT CheckboxCell hinders selection in CellTable
body: <p>I discovered that if you have a GWT <code>CellTable</code> and add a column that contains a <code>CheckboxCell</code>, the selection via a <code>SingleSelectionModel</code> does not work anymore. This cell type does hinder the row selection.
  Following a code sample that demonstrates this behaviour in 2.5.0.rc1.</p>
  
  <pre class="lang-java prettyprint-override"><code>final CellTable&lt;LicenseDto&gt; licenseTable = new CellTable&lt;LicenseDto&gt;();
  final SingleSelectionModel&lt;LicenseDto&gt; selectionModel = new SingleSelectionModel&lt;LicenseDto&gt;();
  licenseTable.setSelectionModel(selectionModel);
  
  
  //--- If I add this column, the selection does work.
  Column&lt;LicenseDto, String&gt; workingColumn = new Column&lt;LicenseDto, String&gt;(new TextCell()) {
  
      @Override
      public String getValue(LicenseDto object) {
          return "Works";
      }
  };
  workingColumn.setFieldUpdater(new FieldUpdater&lt;LicenseDto, String&gt;() {
  
      @Override
      public void update(int index, LicenseDto object, String value) {
          ;
      }
  });
  licenseTable.addColumn(workingColumn);
  
  
  //--- If I add this column, the selection does NOT work anymore.
  Column&lt;LicenseDto, Boolean&gt; notWorkingColumn = new Column&lt;LicenseDto, Boolean&gt;(new CheckboxCell(true, true)) {
  
      @Override
      public Boolean getValue(LicenseDto object) {
          return object.getEnabled();
      }
  };
  notWorkingColumn.setFieldUpdater(new FieldUpdater&lt;LicenseDto, Boolean&gt;() {
  
      @Override
      public void update(int index, LicenseDto object, Boolean value) {
          presenter.enableLicense(object, value);
      }
  });
  licenseTable.addColumn(notWorkingColumn);
  
  initWidget(licenseTable);
  </code></pre>
  
  <p>You can combine multiple cells and add them to the table (e.g. <code>LinkActionCell</code> etc). As long as there is no <code>CheckboxCell</code>, the blue selection with the <code>SingleSelectionModel</code> works like a charm. Does anyone see what I do wrong with this <code>CheckboxCell</code> or is there a bug?</p>