Achtung, die Kurve! in JavaScript v0.4

• Add settings menu.
  • Cursor visibility.
  • Edge fix (for when the monitor and the game have identical height and/or width).
  • What messages to show.
• Add simple unload blocker (to avoid mid-game unload by user mistake).
• Add Browser Safe Mode (meaning the game is run in its own window without history so as to avoid accidental tab switching or history navigation).
• Add exception handling for saving/loading of settings (so the app does not crash if the browser denies access to localStorage).