FlightGear - Flight Simulator FGAddon

* b25j-yasim.xml: delete; was identical to b25-yasim.xml.
* b25j-set.xml: use b25-yasim.xml.
* b25-yasim.xml:
- <propeller/moment>: the rod method should use the mass of a single blade, not the
entire propeller, before multiplying by the number of blades.
- <propeller/takeoff-rpm>, <propeller/takeoff-power>: add.
- <propeller/mass>: correct; add the mass of the propeller too.
- <ballast>: adjust to keep CoG approximately at 25% MAC.
* Models/Interior/Panel/Pedestal/console.xml: use property-cycle for the supercharger
speeds. The POH states that the pilot should shift speeds quickly and decisively.
* Nasal/b25.nas: delete the handling of the boost property of engines.
* Systems/b25-keyboard.xml, Systems/help.xml: Alt+S to shift supercharger speeds.