Convert to new unit APIs, remove old APIs.

There are probably plenty of raw ints around that never used the old
conversion APIs, but we'll just need to fix those when we see them.

Fixes https://github.com/Khopa/dcs_liberation/issues/558

gen/flights/flight.py

@@ -106,7 +106,7 @@ class FlightWaypoint:
     def from_pydcs(cls, point: MovingPoint,
                    from_cp: ControlPoint) -> "FlightWaypoint":
         waypoint = FlightWaypoint(FlightWaypointType.NAV, point.position.x,
-                                  point.position.y, point.alt)
+                                  point.position.y, meters(point.alt))
         waypoint.alt_type = point.alt_type
         # Other actions exist... but none of them *should* be the first
         # waypoint for a flight.