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