Call refreshDisplay() after editing a dive

We now can change the dive date and the order of dives could have changed.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
Add "merge selected dives" to dive list popup menu

This is fairly straight forward. What I dislike is the check for the magic
number of "14 indeces". I'm sure there's a better way to tell if more than
one dive is selected...

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