title: EXTJS Store load callback issue
body: <p>I load my store as follows:</p>
  
  <pre><code>store.load({
      params: {
          paramMap
      },
      callback: function(records, options, success) {
          if (success) {
              var form = formPanel.getForm();
              var jsonStr = Ext.JSON.encode(records[0].raw);
              var jsonObj = Ext.JSON.decode(jsonStr);
              form.loadRecord(jsonObj);
          }
      }
  });
  </code></pre>
  
  <p>The thing is I only want this call back to fire the first time the store is loaded. I want to remove it after that so that when I reload or load the store again it doesn't call this callback again. </p>
  
  <p>Any idea, I tried getting the callback in the options config but that doesn't seem to work.</p>