Partially fix dive downloading

The Qt branch didn't set the preexisting dive count, so matching old
dives didn't work and it always downloaded all of them.

Also, we need to autogroup dives before displaying them if autogrouping
is on.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>