Make double-clicking on the dive list bring up the dive editor

Now that the dive info window is read-only, we need to edit the dives
some other way.  We bring up a dive info edit dialog when you
double-click on the dive list entry for that dive.

I do want to have an "edit" button or keyboard shortcut or something
too, though.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>