Train Stations tutorial — Distributrains Steam update #1620565

Added a tutorial to explain some of the mysteries of how Train Stations work Slightly reduced the difficulty of the Cementmonger victory condition Sliders for setting starting resources in Custom Game now have finer granularity at low numbers Fixed a bug where the Ports could interfere with each other during map generation Fixed a bug where the text colour of the resource counters on the top bar would be incorrect if loading a game immediately after an error message box was displayed