A lot of improvements

Approximate change list:

• Improved illumination
• Added refraction and reflection
• Added custom texture support to compute shaders
• New animated flag with custom texture support
• Removed initial resolution choice menu
• Added a new first launch choice menu with rendering and language options
• New settings menu, in-game rendering options
• Ability to edit shaders in real-time
• Multiple shader pipelines support
• AMD GPU compilation bug-fix
• Music and sounds work properly with variable volume
• A lot of tiny bug fixes