Planner: remove infobox overlay and enable calculated ceiling

Make the infobox invisible in planner (it really doesn't provide a lot of
useful info while planning a dive and more likely gets in the way).
Make the calculated ceiling always visible in planner and add mode.

Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>