title: In ExtJS 4.0, how to config several "feature"s in a grid and toggle among them?
body: <pre><code>var groupingFeature = Ext.create('Ext.grid.feature.Grouping'); 
  Ext.create('Ext.grid.Panel', {
       // other options
       features: [groupingFeature]
  }); 
  </code></pre>
  
  <p>Can I add a new feature into the [groupingFeature] array? How can I do it?</p>
  
  <p>And if there are several features, how can I toggle among them?</p>
  
  <hr>
  
  <p>Now I know how to set several features (but I'm not sure wether this way is correct or not):</p>
  
  <pre><code>var groupingFeature = Ext.create('Ext.grid.feature.Grouping',{
    id: 'group',
    ftype: 'groupingsummary',
    groupHeaderTpl: '{name}',
    hideGroupedHeader: true,
    enableGroupingMenu: false
  });
  var abstractSummaryFeature = Ext.create('Ext.grid.feature.AbstractSummary',{
    id: 'summary',
    ftype: 'abstractsummary',
    hideGroupedHeader: false,
    enableGroupingMenu: true
  });
  Ext.create('Ext.grid.Panel', {
       // other options
        dockedItems: [{
            dock: 'top',
            xtype: 'toolbar',
            items: [{
                tooltip: 'Change the feature',
                text: 'Change',
                handler: function(){
                    var view = Ext.getCmp('sell_quote_item_grid').getView();
                    view.getFeature('group').disable();//someone says I can toggle in this way,
                    view.getFeature('summary').enable();//I tried but failed...
                    view.refresh();
                }
            }]
        }],
       features: [groupingFeature, abstractSummaryFeature]
  });  
  </code></pre>