implement undo method
Merge branch 'ZombieStorage' into mainlogic

Conflicts:
	ZombieLog.0.0.txt
	ZombieLog.1.0.txt
	ZombieLog.1.1.txt
	ZombieLog.2.0.txt
	ZombieLog.3.0.txt
	ZombieStorage.txt
update viewagenda and taskclash functions