Adding Functionality to Remove individual Objects or All objects tied to a Priority.
Merge branch 'master' of https://github.com/SEPR13-SAW/Plane-Panic

Conflicts:
	src/main/java/com/planepanic/game/gfx/screens/Game.java
Merge branch 'master' into Plane-Panic-Ben

Conflicts:
	src/main/java/com/planepanic/game/gfx/DrawThread.java
	src/main/java/com/planepanic/game/gfx/screens/Game.java