game entry file names changed to canonical version

games/rails_an_18xx_game_system.md

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+# Rails: an 18xx game system
+
+_Rails is a Java game engine intended to play any of the 18xx series of turn-based board games._
+
+- Home: https://rails.sourceforge.io/, https://sourceforge.net/projects/rails/
+- State: mature
+- Download: https://sourceforge.net/projects/rails/files/Rails/
+- Keywords: strategy, turn-based
+- Code repository: https://github.com/Rails-18xx/Rails.git
+- Code language: Java
+- Code license: GPL-2.0
+
+## Building
+
+- Build system: Maven
+