Planned dives were still added by directly calling core code.
This could confuse the undo-machinery, leading to crashes.
Instead, use the proper undo-command. The problem is that as
opposed to the other AddDive-commands, planned dives may
belong to a trip. Thus, the interface to the AddDive command
was changed to respect the divetrip field. Make sure that
the other callers reset that field (actually, it should never
be set). Add a comment describing the perhaps surprising
interface (the passed-in dive, usually displayed dive, is
reset).
Moreover, a dive cloned in the planner is not assigned a
new number. Thus, add an argument to the AddDive-command,
which expresses whether a new number should be generated
for the to-be-added dive.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>