title: Extjs sorting store by alphanumeric field
body: <p>I've got a bunch of records whose names are like "Itemtype #", and when they are outputted into a tree view, they're sorted incorrectly, like so:</p>
  
  <ul>
  <li>Item 1</li>
  <li>Item 10</li>
  <li>Item 11</li>
  <li>Item 12</li>
  <li>Item 13</li>
  <li>Item 2</li>
  <li>Item 3</li>
  <li>Item 4</li>
  </ul>
  
  <p>My model fields are defined as follows, and I am sorting on "Name":</p>
  
  <pre><code>fields: [
    { name: 'Id', defaultValue: 0, type: 'int', mapping: 'Id' },
    { name: 'Name', defaultValue: '', type: 'string', mapping: 'Name', sortType: Ext.data.SortTypes.asUCString },
    { name: 'Type', defaultValue: 0, type: 'int', mapping: 'Type' },
    { name: 'CreationDate', type: 'date', mapping: 'CreationDate' }
  ],
  </code></pre>
  
  <p>Can anybody point me in the right direction? I'm using extjs 4.0.5</p>