Support encoding of Transfer-Encoding: chunked

[jfallows]

...in SourceOutputStream / ClientConnectStream
...and TargetOutputEstablishedStream / ServerAcceptReplyStream.

[cmebarrow]

My chunked.transfer.encoding branch has a preliminary implementation for SourceOutputStream. Tests and code need to be added to handle case where target window is insufficient to write out an incoming data frame because of the extra bytes needed for chunk size line (size+CRLF) and terminator CRLF), or to write the last chunk in processEnd.

[jfallows]

@cmebarrow is Transfer-Encoding: chunked supported by both HTTP/1.1 responses and HTTP/1.1 requests?

[cmebarrow]

Yes it can be used in both. This is implied for example in https://tools.ietf.org/html/rfc7230#section-3.3.3.