[Proposal] Queued cookies

Sometimes you want to set a cookie in a class that's not directly sending a response.  This pull request implements Cookie::queue($cookie) to do that.  It essentially does what is (was) done in the Auth\Guard class: creates an array of queued cookies which an after filter (now in the CookieServiceProvider) bundles up with the response.

This pull request also updates the Auth classes to use the new queue() method.