Removed Serialize from all RPC functions, replacing all occurrences with the Message type instance. This was as a result of discovering that the use of Serialize made it easy for application writers to assume too much about courier's behavior, and ultimately cause courier to attempt to decode messages of a different type than encoded into the message. While the use of message values does put more work on the application writer, the work was already there and is outside the scope of problems courier was meant to address.