This teaches the dctool about the subsurface special field strings, and
saves them in the xml output in a way which is compatible with
subsurface.
Signed-off-by: Anton Lundin <glance@acc.umu.se>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Libdivecomputer always uses metric units internally. But when reverse
engineering a device that stores everything using imperial units, it's
very convenient to be able to switch the output to imperial units too.
