Serialized GUI slots so you can now have multiple icons that use the same block. Fixed the config to come with a proper default durability. It isn't supposed to have ' ' around the number. Durability is also checked in the GUI so multiple icons with the same block type but different durability value won't trigger each other.

In case anyone was wondering, you can "fudge" the GUI hash code argument if you want to open it on a player manually. The message remover won't work because the hash is made up, but the other icon buttons will work fine.