Added  modules for writing new transports and endpoints.

Transport          - Base class for all transports
SimpleTransport    - Base for connectionless transport types
ConnectedTransport - Base for connection-oriented transport types

For sending and receive messages:
Endpoint           - Base class for Consumer and Producer
MessageSource      - The basic wrapper for exchanging messages.
Consumer           - Pulls messages from a queue.
Producer           - Sends messages to a topic.

Also provides tests to verify the new code.