First pass to parse uemis Zurich '.SDA' files

This is missing a ton of the information in the .SDA files It only
parses the divelog.SDA file, not the dive.SDA file It ignores the
information on the gas(es) used and all the data on the tanks.

It still draws some strange artefacts at the end of the dive

But it correctly hooks into the import dialogue, it gives you a file
select box (somewhere, I'm sure, a gtk developer cries quietly) and then
parses enough of this file to serve as a proof of concept.

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