title: Implement Json.NET in WCF Message Formatter
body: <p>I'm trying to replace the Json converter that is used by WCF with an open
  source Json.NET (<a href="http://json.codeplex.com" rel="noreferrer">http://json.codeplex.com</a>) mainly due the need to serialize
  objects with circular references [DataContract(IsReference=true)] I tried 
  to inject it in custom IDispatchMessageFormatter with no success. Has anyone
  encounter in this kind of customization? Do you know where can I get a sample 
  or reference to depend on?</p>
  
  <p>Thanks</p>