Adding images and functions to GameBuilder.java

11/6/14: Mainly updating GameBuilder.java and Laser.java

Changes:
GameBuilder.java:
*Worked on spawnPlayers() that will randomly place players in the
corners.

*buildVS() is for vs mode and will call spawnPlayers()

Laser.java:
*Added wallSearch() which recursively searches for a wall that this
laser is colliding with.

MainGame.java:
*Starting to load images.