Squashing 8 commits by DanAlbert:
- Track theater in ControlPoint.
Simplifies finding the owning theater of a control point. Not used yet.
- Clean some cruft out of FlightPlanBuilder.
- Clean up silly some exception handling.
- Move FlightPlan instantiation into the builder.
I'm working on moving the builder to be owned by the Flight, which will simplify callers that need to create (or recreate) flight plans for a flight.
- Simplify IBuilder constructor.
We have access to the theater via the flight's departure airbase now.
- Move FlightPlan creation into Flight.
For now this is just a callsite cleanup. Later, this will make it easier
to separate unscheduled and scheduled flights into different classes without complicating the layout/scheduling.
- Remove superfluous constructors.
- Remove unused Package field.
This appears to be incompatible with pyinstaller. I get the following
when trying to run the executable generated with pyside6:
```
Traceback (most recent call last):
File "qt_ui\main.py", line 29, in <module>
File "PyInstaller\loader\pyimod03_importers.py", line 476, in exec_module
File "qt_ui\windows\QLiberationWindow.py", line 28, in <module>
File "PyInstaller\loader\pyimod03_importers.py", line 476, in exec_module
File "qt_ui\widgets\map\QLiberationMap.py", line 11, in <module>
ImportError: could not import module 'PySide6.QtPrintSupport'
```
