On desktop, we have two CylindersModel concurrently: One in the
planner and one on the equipment-tab. They act differently, because
the former modifies displayed_dive directly, the latter issues
undo commands.
To differentiate, we used the in_planner() function. However, that
appears extremely brittle, especially when combined with undo-commands.
Therefore when generating the model, pass in a parameter that says
whether this is for the planner or the equipment tab and use
that flag to decide how to act.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>