Cleanup
Widened white lasers
Implemented origins into Explosion's Billboard sprite.
Fixed projectile incomplete reset bug (10 explosions then nothing)
Added billboard size per-explosion type
Implemented type-specific framerates for explosions
Fixed billboard dark-rectangle bug
Added support for 2d rotation around camera lookAt vector
Explosions randomly rotated when practical.
Implemented darkIsClear palette on explosions and lasers.