Added support for background music in InGameState.java
Added music file.
Top-down shadow from player

Added a shadow from the player to the platforms. PssmShadowRenderer is
setup in InGameState.initLights(), and the Player and Platform classes
set their own shadow settings.
Small fixes with platform movement

Edited the platform placement code (in PlatformController and update()
loop) to make sure the PlatformDistance is actually the distance
between platforms.
Made instance variables local

Made playerLightPosition, playerSpot and directionToPlayer local
instead of instance variables, now that they are not needed in the
InGameState update loop. Also adjusted the swing of the light somewhat.
Improved SpotLightControl

Improved the light movement, made defaultPositionOffset (of the light)
customisable (added a setter).
Cleaned up some commented-out code in InGameState initLights().
Added music, adjusted light

Merged in Dagen's music code