The only remaining use of the tripflag was to mark dives that were removed explicitly from a trip, i.e. shouldn't be autogrouped. Therefore replace the enum by a simple boolean. Currently, there is no way of unsetting the notrip flag. But this shouldn't result in a user-visible change. Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>