optimised parameter for slingshotelement and bumpers
Merge branch 'master' of https://github.com/paras1/ch.bfh.bti7301.pinball

Conflicts:
	P1_Pinball/src/ch/bfh/bti7301/pinball/screens/LevelScreen.java
	P1_Pinball/src/ch/bfh/bti7301/pinball/screens/Menu.java