Merged HTTP Response and Reply into Request.

Merged HTTP Response and Reply into Request.

Splitting HTTP functionality into 3 objects Request, Response and Reply
introduced a lot of confusion as to which method should belong to which object.

New members of Request:
- req.status (res.status)
- req.parent (reply.parent)
- req.requestBody (req.body)
- req.responseBody (reply.body)
- req.headersIn (req.headers)
- req.headersOut (res.headers)
- req.sendHeader() (res.sendHeader())
- req.send() (res.send())
- req.finish() (res.finish())
- req.return() (res.return())

Deprecated members of Request:
- req.body (use req.requestBody or req.responseBody)
- req.headers (use req.headersIn or req.headersOut)
- req.response

Response is remained in place for backward compatibility and will be removed in
the following releases.  Reply is replaced with Request in the req.subrequest()
callback.  The deprecated properties will be removed in the following releases.