Automatic merge of T1.5.1-1689-g72674c98d and 14 pull requests

- Pull request #900 at 4629736: DMI in 3D cab + two more dials
- Pull request #1030 at d3ae4a2: Refactor settings, in prep for settings exporter
- Pull request #1045 at cc4d53c: Bugfix: Empty Start Time for Explore, and other issues loading from Menu Selection and Content Routes
- Pull request #1052 at d3f00a1: Content Manager: Add axle count, and lowest derail force
- Pull request #1062 at 3b18c48: Train Forces popup Window.
- Pull request #1064 at 53dd604: Add Train Info tab to Help window (F1)
- Pull request #1066 at 62c89c1: Log derailment, using TraceInformation.
- Pull request #892 at 1f5ba4c: Signal Function OPP_SIG_ID_TRAINPATH
- Pull request #1000 at d8d9709: Locomotive operation from control car
- Pull request #1029 at 92c74ef: Superelevation Follow Up Fixes
- Pull request #1057 at d6bd4e3: Switchable brake system
- Pull request #1065 at 409064d: Fix for PantographToggle sound event
- Pull request #1068 at d6e1f83: Build for online-only documentation files
- Pull request #896 at f1681df: First implementation of https://blueprints.launchpad.net/or/+spec/specific-sounds-for-ai-trains

Author: openrails-bot