Add threat zone modeling.

Creates threat zones around airfields and non-trivial air defenses (it's
not worth dodging anything with a threat range under 3nm). These threat
zones can be used to aid mission planning and waypoint placement.

https://github.com/Khopa/dcs_liberation/issues/292

qt_ui/windows/QLiberationWindow.py

@@ -257,8 +257,6 @@ class QLiberationWindow(QMainWindow):
 
     def setGame(self, game: Optional[Game]):
         try:
-            if game is not None:
-                game.on_load()
             self.game = game
             if self.info_panel is not None:
                 self.info_panel.setGame(game)