Settings screen

[mingli1]

• Add a settings screen that is linked from the main menu and the pause dialog (shared screen but accessing from the pause dialog should persist the game state)
• Sliders for sound, music volume, etc
• Check boxes:
  • show fps
  • mute sounds or music
  • show particles
  • show health bars
  • show hints on start, etc
• Drop down box for screen resolution on desktop?