Don't delesect dives, when unregistering them from the backend.
If a previously selected dive is added, select it in the dive-list.
For this purpose introduce a SELECTED_ROLE to query the DiveTripModel
for selected dives.
Unfortunately, when adding multiple selected dives, current_dive_changed
is called for each of them, making this very slow. This will have
to be fixed in subsequent commits.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
0d98da5261