Messages should be Serializable

Since a Message (e.g. in JSF later) might get serialized pretty often, we should make all the Message system Serializable. This includes to move the arguments from Object... to Serializable...

This is needed if you e.g. hold a Message in a @ViewScoped bean, if you like to store the Message in a database, if you use JSF with ClientSide State Saving, etcH