Success : Delete a Category Item
Success : Android sqlite3 not support foreign key cascade delete by default.
		 So to make the functions
Modify : Setting Category List does not show None("없음") item
	      Setting Category List block a long press of ADD("추가하기") item because It can not be deleted.
Modify : Fix that displays the date the ToDo List item is incorrect
Merge branch 'ToDoList' into Setting