THRIFT-894. java: Make default accessors for binary fields return byte[]; provide...

THRIFT-894. java: Make default accessors for binary fields return byte[]; provide new accessors to get ByteBuffer version

This patch causes the underlying ByteBuffer that backs a binary field to be hidden behind a default accessor that provides a byte[] interface. This should allow users who skipped 0.4 to update their generated code without breaking any of their other code. A new accessor has been added that allows a way down to the underlying ByteBuffer for those experts who want to take advantage.

git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@996579 13f79535-47bb-0310-9956-ffa450edef68