Basic Sound Effects and New Controls

-Added Basic Sound Effects
-Changed controls to be camera relative instead of ship orientation
relative
-Reorganized some objects
-Nested Enemy Manager in Planet s.t. planets are natural enemy
generators
-Slight modifications to test level (variable gravity based on planet
size)

Open Bugs:
-Enemies overlapping significantly causes lag

TODO:
-Continue going through 30 improvements
-Generate level from random seed
-Main menu