Stagger package start times.

Avoids crowding the taxiways, and adds some life to the end of the
mission.

Later on, this will happen more naturally because we can delay
takeoffs to align with the package's DTOT.

qt_ui/windows/mission/flight/QFlightCreator.py

@@ -27,6 +27,7 @@ class QFlightCreator(QDialog):
         super().__init__()
 
         self.game = game
+        self.package = package
 
         self.setWindowTitle("Create flight")
         self.setWindowIcon(EVENT_ICONS["strike"])
@@ -90,6 +91,7 @@ class QFlightCreator(QDialog):
         size = self.flight_size_spinner.value()
 
         flight = Flight(aircraft, size, origin, task)
+        flight.scheduled_in = self.package.delay
 
         # noinspection PyUnresolvedReferences
         self.created.emit(flight)