Gas was printed in permille, use gasname instead

After the switch to a central event decoder and just return gasmix from
that we printed things in permille, eg. EAN1000 and 180/550 which looks
kinda strange.
This fixes that by using gasname instead to give the gas a name.

Signed-off-by: Anton Lundin <glance@acc.umu.se>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>