We should support creation of Encoders and Decoders for POJOs so that they can be converted into Websocket Messages.

This needs to be done with the message mediatype in mind. For instance, if we are to produce JSON messages, we should generate encoders and decoders that support different APIs, but notably one that uses the new JSON-P API (possibly supporting both object and stream based APIs). Likewise, for XML, we should support several APIs to marshal/unmarshal messages of type XML.