Automatic merge of T1.5.1-947-g34e078c205 and 16 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 #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 6b9fca4: 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 fc1ac91: Add curve squeal to route
- Pull request #924 at 6c2c3cd: Default Asset Improvements
- Pull request #927 at a28da45: AI Train Power Supply/Lights Fix
- Pull request #929 at a406a69: Add support for common circuit breaker variants
- Pull request #938 at ebe8047: Fix Missing Initializations From Copy in MSTSWagon.cs

Author: openrails-bot