ObdGatewayService: An Android service running in the backend, connecting
bluetooth and send & receive data
reserve the interface to send result from OBD to external server
upload wiki definition
http://en.wikipedia.org/wiki/OBD-II_PIDs#Bitwise_encoded_PIDs
implement upload function
add http handler
fix nullpointer issue when oldcommand response returns.
fix conflict of ObdCommand.java