Automatic merge of T1.5-rc1-41-g3023eb3df and 12 pull requests

- Pull request #570 at 824f96f: Experimental glTF 2.0 support with PBR lighting
- Pull request #630 at 704731a: Sky Color Fix (Addresses Trello Roadmap Card #367 for More accurate sunrise and sunset)
- Pull request #650 at 0106424: Renewed Russian translation up to 1.5-rc1 version
- Pull request #652 at 918fdb1: Add button functions to Raildriver
- Pull request #677 at 9d5fb93: Correct double heading bug
- Pull request #688 at e44897d: adds Help Icons to Video tab
- Pull request #690 at 3399d4b: Sync turntables and transfertables in multiplayer mode
- Pull request #692 at c82a76d: Italian translation for OR 1.5
- Pull request #699 at 6baf43d: Bug fix for https://bugs.launchpad.net/or/+bug/1987453. Web: HUD/Force Information, some labels not visible.
- Pull request #701 at 757b1be: Prevent train from going to manual mode from an explorer activity
- Pull request #702 at ea8c6f0: Bug fix for https://bugs.launchpad.net/or/+bug/1987504 Server can't throw switches for clients in multiplayer
- Pull request #703 at 6b61997: Add default signal function in case of SIGCFG errors

Source/Orts.Simulation/Simulation/Signalling/SignalHead.cs

@@ -50,7 +50,7 @@ public class SignalHead
         public float? ApproachControlLimitPositionM;
         public float? ApproachControlLimitSpeedMpS;
 
-        public SignalFunction Function { get; protected set; }
+        public SignalFunction Function { get; protected set; } = SignalFunction.UNKNOWN;
 
         public int ORTSNormalSubtypeIndex;     // subtype index form sigcfg file
 
@@ -156,7 +156,6 @@ public void SetSignalType(TrItem[] TrItems, SignalConfigurationFile sigCFG)
                 }
                 else
                 {
-                    Function = SignalFunction.UNKNOWN;
                     Trace.TraceWarning("SignalObject trItem={0}, trackNode={1} has SignalHead with undefined SignalType {2}.",
                                   mainSignal.trItem, mainSignal.trackNode, sigItem.SignalType);
                 }