Save axle integrator status

Author: cesarBLG

Source/Orts.Simulation/Simulation/RollingStocks/SubSystems/PowerTransmissions/Axle.cs

@@ -677,6 +677,8 @@ public void Restore(BinaryReader inf)
             previousSlipSpeedMpS = inf.ReadSingle();
             AxleForceN = inf.ReadSingle();
             AxleSpeedMpS = inf.ReadSingle();
+            NumOfSubstepsPS = inf.ReadInt32();
+            integratorError = inf.ReadSingle();
         }
 
         /// <summary>
@@ -689,6 +691,8 @@ public void Save(BinaryWriter outf)
             outf.Write(previousSlipSpeedMpS);
             outf.Write(AxleForceN);
             outf.Write(AxleSpeedMpS);
+            outf.Write(NumOfSubstepsPS);
+            outf.Write(integratorError);
         }
 
         /// <summary>