Automatic merge of T1.5.1-925-g1c557094e and 20 pull requests

- Pull request #570 at 3539862: Experimental glTF 2.0 support with PBR lighting
- Pull request #799 at dfc715e: Consolidated wind simulation
- Pull request #839 at d00beb9: First phase of https://blueprints.launchpad.net/or/+spec/additional-cruise-control-parameters
- Pull request #876 at f92de76: docs: add source for documents previously on website to source Documentation folder
- Pull request #882 at 3ca0eb1: Blueprint/train car operations UI window
- Pull request #885 at 0a956f5: feat: Add notifications to Menu
- Pull request #886 at 6c0785b: Scene viewer extension to TrackViewer
- Pull request #892 at 1f5ba4c: Signal Function OPP_SIG_ID_TRAINPATH
- Pull request #896 at 5866028: First implementation of https://blueprints.launchpad.net/or/+spec/specific-sounds-for-ai-trains
- Pull request #903 at 7af1f91: Downloading route content (Github, zip)
- Pull request #912 at f7b85e4: New Triple Valve Features Vol. 2
- Pull request #919 at 26cc6a8: Added mouse wheel support for controls which can be moved by pressing t…
- Pull request #923 at cc1b5b6: Add curve squeal to route
- Pull request #924 at 6c2c3cd: Default Asset Improvements
- Pull request #925 at e3b1688: Fix brakeshoe force bug
- Pull request #927 at 7bce293: AI Train Power Supply/Lights Fix
- Pull request #929 at a406a69: Add support for common circuit breaker variants
- Pull request #930 at 42398f4: Further enhancements for duplex locoomotive
- Pull request #932 at 9bdb074: Changed matrix's to matrices
- Pull request #933 at a3f56f4: Fix AI DM crashing

Author: openrails-bot

Source/Orts.Simulation/Simulation/RollingStocks/MSTSLocomotive.cs

@@ -2017,9 +2017,6 @@ public override void Update(float elapsedClockSeconds)
 
             // Pass Gearbox commands
 
-
-
-
             // Note - at the moment there is only one GearBox Controller created, but a gearbox for each diesel engine is created. 
             // This code keeps all gearboxes in the locomotive aligned with the first engine and gearbox.
             if (gearloco != null && gearloco.DieselTransmissionType == MSTSDieselLocomotive.DieselTransmissionTypes.Mechanic && GearBoxController.CurrentNotch != previousChangedGearBoxNotch)
@@ -2158,8 +2155,13 @@ public override void Update(float elapsedClockSeconds)
                                     if (de.State != DieselEngineState.Running)
                                         de.Initialize();
                                 }
+
+                                // if train is a geared locomotive then set it to automatic operation as AI driver can't operate manual gearboxes
                                 if (de.GearBox != null)
                                     de.GearBox.GearBoxOperation = GearBoxOperation.Automatic;
+
+                                // Set gear to "low gear" at start.
+                                de.GearBox.currentGearIndex = de.GearBox.NumOfGears - 1;
                             }
                         }
                     }