Refactorizada forma de cargar sprites de entities para utilizar
ResourceManager

Cambiados loaders de Player y Zombie para que sus metodos sean estaticos
Merge branch 'master' of https://github.com/JaumeRibas/Shooter2D.git

Conflicts:
	Shooter2D/src/org/escoladeltreball/shooter2d/MainActivity.java
	Shooter2D/src/org/escoladeltreball/shooter2d/constants/SpriteConstants.java