Automatic merge of T1.6-rc3-30-gdf7bf1a26 and 12 pull requests

- Pull request #1104 at c039a26: Handle simple adhesion within the axle module
- Pull request #1057 at 1c2bcb4: Switchable brake system
- Pull request #1086 at e10390b: Add Settings Exporter tool (copy settings to INI, etc)
- Pull request #1091 at 7fc8de1: Automatic speed control
- Pull request #1110 at 387388e: Fix Activity Runner persists after loading exception
- Pull request #1115 at 270f22f: Do not activate ETS switch if no suitable cars are attached
- Pull request #1121 at 91d2d26: Manually Override Articulation
- Pull request #1123 at dc286f5: Handle null control active locomotive
- Pull request #1125 at 7a4f055: Lift #1096 into 1.6 release
- Pull request #1082 at 5845a1a: Allow variable water level in glass gauge
- Pull request #1081 at 689494b: Brake cuts power unification
- Pull request #1124 at fab5457: Built-in PBL2 brake controller

Author: openrails-bot

Source/Orts.Simulation/Simulation/RollingStocks/SubSystems/CruiseControl.cs

@@ -796,7 +796,7 @@ public void Save(BinaryWriter outf)
             outf.Write(DynamicBrakePriority);
             outf.Write((int)SpeedRegMode);
             outf.Write((int)SpeedSelMode);
-            outf.Write(TrainBrakePercent);
+            outf.Write(TrainBrakePercent ?? -1);
             outf.Write(TrainLengthMeters);
             outf.Write(CCIsUsingTrainBrake);
         }
@@ -814,6 +814,7 @@ public void Restore(BinaryReader inf)
             SpeedRegMode = (SpeedRegulatorMode)inf.ReadInt32();
             SpeedSelMode = (SpeedSelectorMode)inf.ReadInt32();
             TrainBrakePercent = inf.ReadSingle();
+            if (TrainBrakePercent < 0) TrainBrakePercent = null;
             TrainLengthMeters = inf.ReadInt32();
             CCIsUsingTrainBrake = inf.ReadBoolean();
         }