Put all the logic handling adding/removing/contains there and encapsulate our List
Additionally, should prevent a ConcurrentModificationException by locking, but I'm not 100% on the contiains not throing such an exception.
Given Bukkit's behavior of events, it would have never been possible for more than one player's data to occupy the shared arraylist... Still looked ugly, though.
Also helps toward concurrent events, should they ever come.
Also moved from a static boolean flag to a per-use flag
Also removed unused static variable "w"