title: Magento 1.9 set the order for multiple select attribute product
body: <p>I've created a new product attribute of type multiple select from a predefined list. 
  The problem with multiple select is that I cannot set the order for the selected values into the admin panel. The order is important for the frontend. 
  I've tried to create, without success, a custom renderer for this attribute.</p>
  
  <p>Any suggestions are welcome.</p>
  
  <p>Thanks</p>