Made Chunk implement Retainable, and protocol implementations
to link the RetainableByteBuffer all the way to the Chunk.
Extended Retainable to have both a retain() and a release() methods.
Removed HTTP/2's ISession and IStream, now just using HTTP2Session and HTTP2Stream.
Removed *.Adapter classes in favor of interfaces with default methods.
Javadoc additions and clarifications.
Signed-off-by: Simone Bordet <simone.bordet@gmail.com>
Simone Bordet
Joakim Erdfelt
Greg Wilkins