Use new connection string for constructor

This removes the classical 'bucket', 'host', 'port', etc. options in
favor of the new standardized connection string.

Change-Id: Ia98084f03834b27ab5033f427b18c2e48a6ccaf6
Reviewed-on: http://review.couchbase.org/41302
Reviewed-by: Dave Rigby <daver@couchbase.com>
Reviewed-by: Volker Mische <volker.mische@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>