Added the border texture in sprites
Added Textures POWERUPBOXEs and ShieldPowerUp class. In SpaceShip class
the boolean Shield and get/set methods added.
Merge branch 'master' of https://github.com/Firedroide/AsteroidMiner.git

Conflicts:
	AsteroidMiner/src/ch/kanti_wohlen/asteroidminer/entities/SpaceShip.java