Use configured vertical speed units in ruler

Ruler was hard-coded to use seconds as speed unit. This makes it use
get_vertical_speed_units to switch between seconds and minutes.

Signed-off-by: Anton Lundin <glance@acc.umu.se>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Get rid of compiler warning on format strings

This gets rid of compiler warnings "format not a string literal and no
format arguments [-Wformat-security]". E.g. when building distribution
packages these warnings are often treated as errors preventing the
build (with good reason).

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Export dives in UDDF format

Implement exporting in UDDF format as was done in Gtk version. File menu
exports all the dives, right click on selection exports the selected
ones.

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Add current date to CSV import

Since CSV import does not include date/time stamp, we need to generate
one for ourselves. This patch uses current time of the import as dive
time.

Signed-off-by: Miika Turkia <miika.turkia@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>