Ignore Nitrox/He seetings when editing cylinders for multiple dives

When figuring out which cylinders to change in a multi-dive edit, we
already ignored the beginning and end pressures. But it turns out to make
more sense to also ignore the Nitrox / Helium settings.

Imagine you do a number of dives - for some reason your dive computer
records the wrong cylinder size in the downloaded logfile (like my uemis
does all the time). Dives will likely have different Nitrox percentage,
but you should still be able to simply fix the cylinder size for all dives
at once.

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>