Gravity Changer Unofficial Port

-Fixed various of entity mixin issues (Arrow, Boat, ClientPlayer)

-Fixed gravity anchor

-Added fancy new texture for all items

-Fixed auto-jump miss judge when using different gravity directions

-Fixed potion & status effect

-Added more language support

-Initial alpha release

-Core gravity mechanism included.
Many item functionally is still in test.
(Currently unobtainable in Creative Tab)