Sync dsn system with latest spec

This provides support for couchbase, couchbases and http

Additionally support for https:// and couchbase+explicit:// are provided
for internal testing purposes.

Change-Id: Ia55b93de29493077f65736afba49426191675770
Reviewed-on: http://review.couchbase.org/38385
Reviewed-by: Brett Lawson <brett19@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>