Implemented GlowMetaLeatherArmor partially completes #77

Hey, 

(See #77)

Just getting into the whole open source thing, thought id start off small. Please let me know if I have made any mistakes.

Thanks,
Bukkit API requires `getDefaultLeatherColor()` on `ItemFactory`, so `GlowItemFactory` is where this constant is kept.

Making the constant package-private instead of private is a little odd but not the worst. `GlowItemFactory.instance().getDefaultLeatherColor()` would also suffice.