New Sprites, New Music!

Changes in v031:

- New background theme "Mysterious Stranger" by David Gonzales music

- Overhauled player sprites.

- Minor Bugfixes.

- Major reorganization & cleanup.

- Dedicated audio bus for sound effects and background music.

- Fixed bug when bullet projectiles go off screen

- Fixed bug when enemy terminators go off screen

- Tuned player movement speed and animation speed

- Revised controls for gamepad and keyboard