cbc: add dsn parsing command

This command will help users understand how their connection string is
being interpreted by the library.

Change-Id: I1823c09c97a7a0479909d340dd62e969c197b543
Reviewed-on: http://review.couchbase.org/38404
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>