Automatic merge of T1.5.1-495-g55f992dcd and 10 pull requests

- Pull request #570 at 7269d24: Experimental glTF 2.0 support with PBR lighting
- Pull request #757 at d9d75f4: Unify RailDriver code implementations
- Pull request #799 at dc03850: Consolidated wind simulation
- Pull request #821 at cc3af66: Adds suppression of safety valves
- Pull request #829 at 434af02: Improvements for air brakes #3 - Emergency valves
- Pull request #831 at 9417e1b: poor mans switch panel on tablet
- Pull request #839 at d00beb9: First phase of https://blueprints.launchpad.net/or/+spec/additional-cruise-control-parameters
- Pull request #846 at 9668051: Initialize cars before restore
- Pull request #849 at 0d4e3da: Contributed projects and forking clarity
- Pull request #850 at 1605667: Correct output of sound system info

Source/Orts.Simulation/Simulation/RollingStocks/SubSystems/PowerSupplies/DieselEngine.cs

@@ -1586,14 +1586,7 @@ public void Restore(BinaryReader inf)
             OutputPowerW = inf.ReadSingle();
             DieselTemperatureDeg = inf.ReadSingle();
             GovernorEnabled = inf.ReadBoolean();
-
-            bool gearSaved = inf.ReadBoolean();  // read boolean which indicates gear data was saved
-
-            if (gearSaved)
-            {
-                GearBox = new GearBox(this);
-                GearBox.Restore(inf);
-            }
+            GearBox?.Restore(inf);
         }
 
         public void Save(BinaryWriter outf)
@@ -1603,16 +1596,7 @@ public void Save(BinaryWriter outf)
             outf.Write(OutputPowerW);
             outf.Write(DieselTemperatureDeg);
             outf.Write(GovernorEnabled);
-
-            if (GearBox != null)
-            {
-                outf.Write(true);
-                GearBox.Save(outf);
-            }
-            else
-            {
-                outf.Write(false);
-            }
+            GearBox?.Save(outf);
         }
 
         /// <summary>