title: fixed width in gxt grid
body: <p>guys i want to fix certain column width ... i want to use setFixed(true)  ... here how i create the column</p>
  
  <pre><code>  private ColumnConfig&lt;ContentAttribute, ContentAttribute&gt; createActionsColumn(int actionsColumnWidth) {
  final BackofficeButtonCompositeCell&lt;ContentAttribute&gt; buttonsCell = new BackofficeButtonCompositeCell&lt;ContentAttribute&gt;(
      createActionsGridCellRenderer().getButtonsCells());
  final DtoValueProvider&lt;ContentAttribute&gt; valueProvider = new DtoValueProvider&lt;ContentAttribute&gt;(ACTIONS_COLUMN_ID);
  return SenchaGridUtils.createDefaultColumnConfig(valueProvider, actionsColumnWidth, MessagesFactory.bo().actions(),
      buttonsCell);
  </code></pre>
  
  <p>}</p>
  
  <p>then how to fix its width ??</p>