Edit delete and done command

Delete -> clears everything
Delete <TaskNum> -> delete task under curr label
Delete <Label> -> delete the specific label and tasks
Delete <Label> <TaskNum> -> delete that task under that label
Merge remote-tracking branch 'origin/master'

Conflicts:
	ToDoThis/todothis.txt
Merge branch 'master' of https://github.com/cs2103aug2014-w14-4j/main