title: Using Sprites in extjs
body: <p>I'm currently working on a project where we recieved all our icons in 1 sprite file. I have never ever used sprites (and i'm pretty new to extjs)
  I cannot find a decent example of how to transform the following code (which uses 1 upload.png) into using a spritefile (icons.png)</p>
  
  <pre><code>{
      xtype: 'actioncolumn',
      cls: 'tasks-icon-column-header tasks-upload-column-header',
      width: 24,
      icon: 'images/upload.png',
      iconCls: 'x-hidden',
      tooltip: 'Upload',
      menuDisabled: true,
      sortable: false
      handler: Ext.bind(me.handleUploadClick, me)
  }
  </code></pre>