FlightGear - Flight Simulator FGAddon

* Increase the rating as follows:
FDM=5. Real-life limitations and behavior are accurately modeled.
Systems=5. Stores and weapons, emergency procedures, gunsight accurately modeled.
Cockpit=4 (unchanged).
Model=4 (unchanged).
* name the fuel tanks.
* rename Models/MiG-15bis-model.xml to Models/MiG-15bis.xml
so that http://mpserver12.org/tracker/aircraft/MiG-15bis/ works
* MiG-15bis-set.xml: allow-toggle-cockpit and toggle auto-coordination with L.
* MiG-15bis.xml: use pressure altitude instead of distance to ground for aerodynamics.
* Models/Instruments/Airspeedometer/MiG-15bis-Airspeedometer.xml: correct the rotation
of the needles: the small needle now correcty indicates hundreds of km/h, the large
needle does a full turn for every 100 km/h and points north for 0 km/h.