title: Using Angularjs UI-Grid rowTemplate to get the plus icon in the row header
body: <p>I have a group and subgroup grid using ui-grid v3.0.0-rc.20-8199eb5 - 2015-04-13. I need the plus and minus icon in the rows that contain data and not the grouping header.  Right now there are none in any rows. I have been trying to use rowTemplate and have only been successful in adding another row header but not modifying the existing row header.</p>
  
  <pre><code> $scope.gridOptions = {
          enableFiltering: true,
          paginationPageSizes: [25, 50, 75],
          paginationPageSize: 25,
          onRegisterApi: function(gridApi) {
              $scope.gridApi = gridApi;
              var cellTemplate = '&lt;div class="ui-grid-row-header-cell ui-grid-expandable-buttons-cell"&gt;&lt;div class="ui-grid-cell-contents"&gt;&lt;i ng-class="{ \'ui-grid-icon-plus-squared\' : !row.isExpanded, \'ui-grid-icon-minus-squared\' : row.isExpanded }" ng-click="grid.api.expandable.toggleRowExpansion(row.entity)"&gt;&lt;/i&gt; &lt;/div&gt;&lt;/div&gt;';
              $scope.gridApi.core.addRowHeaderColumn({ name: 'rowHeaderCol', displayName: '', cellTemplate: cellTemplate });
          },
          enableRowSelection: true,
          enableRowHeaderSelection: false,
          enableGridMenu: true,
          multiSelect: false
      };
  </code></pre>