FlightGear - Flight Simulator FGAddon

The standard properties are not only transmitted over multiplayer but also recorder for replays.
This change therefore restores compatibility of the front gear with replays. Also saves 18 bytes
per mp packet by avoiding 3 unnecessary float properties.

* an24b-set.xml (sim/multiplay/generic/float[1..3],
an2/animations/gear, an2/animations/gear-smalldoors, an2/animations/gear-bigdoors): delete.
* Models/An-24B.xml (nasal/load): delete the aliasing of the deleted properties.
Animate the front gear and its doors using only gear/gear[0]/position-norm.
* Models/Interior/Instruments/Control_Units/Gear/sw_gear-lever.xml: ditto.
* Models/Interior/Instruments/Control_Units/Gear/gear-lever-lock.xml: ditto.
* Tutorials/Engineer-Preflight.xml: ditto.