Airlift support.

UI isn't finished. Bulk transfers where the player doesn't care what
aircraft get used work (though they're chosen with no thought at all),
but being able to plan your own airlift flight isn't here yet.

Cargo planes are not implemented yet.

No way to view the cargo of a flight (will come with the cargo flight
planning UI).

The airlift flight/package creation should probably be moved out of the
UI and into the game code.

AI doesn't use these yet.

https://github.com/Khopa/dcs_liberation/issues/825

game/db.py

@@ -1174,6 +1174,7 @@ EXPANDED_TASK_PAYLOAD_OVERRIDE = {
     "SWEEP": ("CAP HEAVY", "CAP"),
     "OCA_RUNWAY": ("RUNWAY_ATTACK", "RUNWAY_STRIKE", "STRIKE"),
     "OCA_AIRCRAFT": ("OCA", "CAS MAVERICK F", "CAS"),
+    "TRANSPORT": (),
 }
 
 PLANE_PAYLOAD_OVERRIDES: Dict[Type[PlaneType], Dict[Type[Task], str]] = {