Support GCLB Cookies

This forum post outlines a GCLB cookie, used by load-balancers to manage sticky sessions.
https://forums.couchbase.com/t/couldnt-parse-expires-in-cookie/34932/4

My guess is that all we need to do is to copy it in to subsequent requests, if we see it.

ADDED: It sounds as if my guess was wrong.  Apparently we need to parse the expiry date and to stop using a cookie when it expires.

I'm creating separate sub-task tickets for each of the platforms because each has a different implementation for cookie handling.

This task, the parent for all the subtasks, should be the focus for discussion of how the cookies should be handled.  Use the subtasks to discuss platform specific implementation.