Major update with many changes and improvements

Add and change the following:

• add heads up display
• add AI
• add inventory
• simplify one aspect of the communications puzzle
• change how key cards are used
• new UI theme
• add multi hit damage system
• add ambient noise zones
• more enemies
• more lava
• new shader for animated sky with sun and sky with stars
• create ladder mechanic and replace some stairs with ladders
• make the reactor puzzle more challenging
• make the O2 puzzle more challenging
• several performance improvements