Instead of letting the user edit the fields before adding a dive,
simply add an empty dive. Thus, the ADD mode of the main tab can
be removed.
Constructing a new dive with default-depth and making sure that
the dive is displayed correctly is very subtle. This all needs
to be detangled in due course.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
4a3ffeba05