Picture handling: parse and convert old style picture events

Speacial case handling for event type '123' to instead add a picture to
the picture_list of the dive.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Picture handling: switch to stronger typed offset

Also change the on file XML to be even easier to read by making it a
duration as well (which gets us '32:34 min' instead of un-typed seconds).
This is backwards compatible, it will happily read what was written with
the previous commit).

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Dive edit: do a better job noticing when the coordinates were changed

Previously the code could get confused by edits (including trivial things
like deleting the coordinates). It seems much more reliable to simply
compare the coordinates of the edited dive with the ones in the current
dive before the edits.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Fix incorrect argument order for %.*f

Strangely, *prinf() on Linux appears to do the right thing in either
order (my guess is based on the type of the two values?), but on Windows
things go badly.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>