CCBC-500: Allow using simple host:port as a connection string

This allows a host:port combination, with an `http://` implicit scheme.

Change-Id: Ifea6dd0bca849689afbf2495d6ceb0b468136605
Reviewed-on: http://review.couchbase.org/40935
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>