Removed symbols in items' lore and name. Bukkit has a bug and doesn't save special chars. (You can still use the in commands)
Added multi world support:
new node: "give-on-world-change: false" (default = false) if true, players will be given items when switching worlds.
new node: "disabled-worlds: world_nether, world_the_end" (default = none) the player will not receive the item in this worlds, and if his inventory contains it, will be removed.
Added an example in items.yml with all the existing nodes.
