title: can't get the custom grid filter working
body: <p>What i want to do is a filter option in a column of a grid. THis is the column:</p>
  
  <pre><code>{
          id: 'kleuren',
          text: 'Kleuren',
          sortable: true,
          filterable: true,
          minWidth: 60,
          flexible: 0,
          width: 60,
          filter: {
              type: 'list',
              store: kleuren
          },
          renderer: kleurenWeergave,
          dataIndex: 'kleuren'
      }
  </code></pre>
  
  <p>for the store/model i use this</p>
  
  <pre><code>kleurenStore = Ext.create('Ext.data.Store', {
      fields: ['id', 'text'],
      data: kleurenModel
  });
  
   var kleurenModel = [
              ['rood', 'rood'],
              ['groen', 'groen'],
              ['blauw', 'blauw'],
              ['geel', 'geel']
              ]
  </code></pre>
  
  <p>This is my grid now</p>
  
  <pre><code>    var grid = Ext.create('PersistantSelectionGridPanel', {
      autoscroll: true,
      region: 'center',
      store: allLoaded,
      multiSelect: false,
      stateful: true,
      features: [filtersFeature],
      loadMask: false,
      stateId: 'stateGrid',
      viewConfig: {
          stripeRows: true
      },
      columns: [{....
  </code></pre>