title: Reconfigure GridPanel with grouping on GroupingStore
body: <p>I have a problem with a GridPanel that uses a GroupingView:</p>
  
  <pre><code>var grid1 = new Ext.grid.GridPanel({
      store: new Ext.data.GroupingStore({
          fields: [ ]
      }),
      cm: new Ext.grid.ColumnModel([  ]),
      selModel: new Ext.grid.RowSelectionModel({ singleSelect: false }),
      view: new Ext.grid.GroupingView({
          groupTextTpl: '{text} ({[values.rs.length]} {[values.rs.length &gt; 1 ? "' + BPS.Resource.items + '" : "' + BPS.Resource.item + '"]})'
      })
  });
  </code></pre>
  
  <p>I an event I call reconfigure that sets a new store and columnmodel. The store is a GroupingStore and I set what groupField i want to use:</p>
  
  <pre><code>// define the store
  var store1 = new Ext.data.GroupingStore({
      proxy: new Ext.data.HttpProxy({
          url: listConfig.dataURL + '?sort=' + listConfig.defaultSortField + '&amp;dir=' + listConfig.defaultSortDirection,
          method: 'POST'
      }),
      autoLoad: false,
      remoteSort: true,
      remoteGroup: true,
      groupOnSort: false,
      groupField: listConfig.groupingColumn,
      sortInfo: {
          field: listConfig.defaultSortField,
          direction: listConfig.defaultSortDirection
      },
      paramNames: {
          start: 'skip',
          limit: 'take',
          sort: 'sort',
          dir: 'dir'
      },
      reader: new Ext.data.JsonReader()
  });
  
  // reconfigure the grid
  grid1.reconfigure(store1, new Ext.grid.ColumnModel(listConfig.columnDefinitions));
  </code></pre>
  
  <p>However, this seem to work the first time it's loaded. It sets grouping on a column, or no grouping at all if I haven't configured it. But after the user turn off grouping in the gridpanel and the same code runs in order to load the configuration it doesn't change it to be grouped.</p>
  
  <p>What can I do to reconfigure the grid to use, or not use, grouping?</p>