Bukkit

- accepts not only OAK_WALL_SIGN but all Materials, with "wall_sign" in their name, like: ACACIA_WALL_SIGN;BIRCH_WALL_SIGN;DARK_OAK_SIGN;JUNGLE_WALL_SIGN;LEGACY_WALL_SIGN;OAK_WALL_SIGN;SPRUCE_WALL_SIGN