Unregister GameManager Listener on world destroy.
Merge branch 'GameManager-refactor' into deallocateListeners

Conflicts:
	src/main/java/net/SimpleSurvival/GameManager.java
Move unregister to end of process.
Fix double enum.
make listeners world aware
fix the 'everybody dies' glitch
fix the multiplayer invincibility glitch
fix no world end glitch
player visibility fix
change world return location
change player damage conditions