The AI isn't making use of these yet, but it's not smart enough to do so
anyway.
Would benefit from an icon to differentiate it on the map.
I'm stretching the definition of "control point" quite a bit. We might
want to put a class above `ControlPoint` for `AirSpawnLocation` to
represent types of spawn locations that can't be captured and don't have
ground objectives.
Fixes https://github.com/Khopa/dcs_liberation/issues/274
Somehow this constant was wrong so all of our foot-to-meter
conversions were coming out ~7% too large. We're still introducing
some error because we're rounding early rather than only when we need
an integer, but it's much more accurate now.
