Java Go Rpc client first commit

A synchronous Go RPC client in Java.
No support for authentication, streaming and deadlines yet.
Add integration tests to java gorpc client

Fixed issue reading responses when error occurs
Moved all constants to a single file
Added support for MAGIC_VAL in bson codec
Run integration test in verify phase
Renaming package name to com.youtube.vitess.gorpc
Java: add .gitignore at root folder
Better exception handling and log4j in GoRpc client

Have the library log, wrap and rethrow low level errors
Added log4j