Traditionally, the DiveTripModel has its data sorted in opposite
direction to the core-data (chronologically descending vs. ascending).
This bring a number of subtle problems. For example, when filling
the model, trips are filled according to the *last* dive, whereas
later insertion points are according to the ->when value from the
core, which depends on the *first* dive.
As a start of fixing these subtleties, change the sort direction
to reflect the core-data. Ideally, this should lead to a removal
of the redundant data-representation.
Since the model is now sorted in ascending order, sorting has to
be enabled in the DiveListView constructor to reflect the
default-descending order.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
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