Add more static cylinder types - and pick them up from the dive log

This adds a few more predefined cylinder types to the static list, but
perhaps more importantly, if we try to show a cylinder description that
we haven't seen before, we automatically add that description to the
list as well.

This way, if people have their own cylinder types, our cylinder
management will automatically figure them out and make it easy to enter
them.

NOTE! It might be best to add the new cylinder description at dive log
load time, rather than at 'show' time.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>