Bug fixes and more

Change-list:

• Added a cross-eye 3d mode
  
• Added auto-exposure, aka adaptive brightness
• Improved bloom
• Improved shadow upscaling
• Added original shaders as a new configuration
  
• Added NEON shaders
  
• Visual changes to most of the original levels
  
• Improved flag texture mapping
  
• Interface bug-fixes
• Added a credits menu
  
• New pause menu
  
• New settings menu
  
• Added a screenshot sound
• Play next level setting in the editor now works
• Added several new levels