Use the CCR corrected gases for EAD and END calculations

Signed-off-by: Robert C. Helling <helling@atdotde.de>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Change tank editing behavior for multi dive edit

Previously we only applied the type of tank (description, volume, working
pressure) to all selected dives where the tank description matched.

With this patch we also copy the gas mix into all matching cylinders.

Additionally this addresses the issue that we should have a separate copy
of the cylinder description string for each dive.

Fixes #754

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Make sure we don't use the 'changed' flag uninitialized

Valgrind reported this while I was testing the previous commit.

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