Display the correct metric SAC rate in divelist

We were doing integer math by mistake.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Show EANxx for Nitrox in info tab

Showing all gases (except air) as (o2/he) feels a bit odd, most people
would only use the two gas notation if they are actually diving trimix.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>