Make sql.php exit status more informative

Make sql.php exit status more informative

Add a --status option which sets nonzero exit status for a query
returning or updating no rows. This is useful for shell scripts which
want to do simple existence checks (e.g. 'unless' conditions in Puppet)
or need to do a single-row change.

Change-Id: I3988c4fb24251dd8b33ac85aed9d0ae03eb0f910