potions. Addresses BUKKIT-817
- Potion's type can be null
- Add Potion.setType()
- New Potion constructors which do not take a PotionType parameter
- Potion constructor chainers splash() and extend() added
- Add PotionType.getMaxLevel() and PotionType.isInstant()
- Add PotionType.WATER which is a very special case
- Make PotionType.getDamageValue() public
By: Celtic Minstrel <celtic.minstrel.ca@some.place>