title: date format in a grid ext 4.1
body: <p>I'm getting inconstant results with my dates. Sometime they are getting converted to us format. 
  I have the following json</p>
  
  <pre><code>{ "Created":"09/03/12" }
  </code></pre>
  
  <p>In my grid i have</p>
  
  <pre><code>{
    id: 'Created',
    text: "Created",
    dataIndex: 'Created',
    xtype: 'datecolumn',
    format: 'd/m/y',
    width: 150,
    sortable: true,
    field: {
      xtype: 'datefield',
      allowBlank: false,
      format: 'd/m/y'
    }
  },
  </code></pre>
  
  <p>So i want to display</p>
  
  <p><code>09/03/12</code> (9th March) 
  but i'm getting <code>03/09/12</code></p>