Added HexDump class from Android Project.

This class is under Apache 2.0 license.
Improved debug output in the TcpHandler class.
Fixed TransportMessageDispatcher and Buffers classes for thread-safe access to the ByteBuffer.

See http://www.javacodegeeks.com/2012/12/the-java-bytebuffer-a-crash-course.html
Fixed generated code in Calculator unit test for thread-safe access to the ByteBuffer.
Improved Calculator unit test.

Added test with multiple threads.