Small whitespace fix

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Picture loading: only add the pictures to "reasonable" dives

If the picture has a timestamp that was within 30 minutes of the start and
finish of the dive, we take it. Otherwise we don't.

If the timestamps of the images are off, the time shift dialog allows the
user to fix this.

And with this patch the user can select all the dives of a trip and all
the pictures they took on the trip and the "right thing" will happen.

Fixes #578

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