Add windsocks to FARPs, kneeboard improvements.

Kneeboard improvements:

* Optional (aircraft specific) metric speeds/distances/altitudes.
* Heading to waypoint.

Fuel still needs to be converted to metric, but good enough for now.

Fixes https://github.com/dcs-liberation/dcs_liberation/issues/915

resources/units/aircraft/Mi-24P.yaml

@@ -19,5 +19,6 @@ manufacturer: Mil
 origin: USSR/Russia
 price: 14
 role: Attack/Transport
+metric_kneeboard: true
 variants:
   Mi-24P Hind-F: {}