Overhaul how transitions are stored in FlightPlan XML, and how
they’re exposed to Nasal. Simplify the Nasal access by making
‘sid_trans’ and ‘star_trans’ writeable.
Extend the unit-tests a lot to cover this, both from C++ and also
from Nasal
As part of this, overhaul the ownership of FlightPlan delegate
factories, to make it safer (use ref-counting of the factories,
and allow the factory to customise delegate clean-up behaviour)
- Fix Leg ownership to avoid segfaults when deleting them via Nasal
- Modify FP save/load code so restrictions and holds are correctly
saved and restored
Extend the tests to cover these cases.
