FlashFyre's Enchantments

- Added Obsidian Skull, an enchantment for helmets which reduces damage when flying into walls using the elytra. Goes up to level 4 and cannot be combined with any protection enchantments. It's also a treasure enchantment.
- Added Butchering, an enchantment for axes which deals increased damage to animals. Goes up to level 3.
- Enchanted books with Obsidian Skull can be found in end city chests.
- Added Curse of Anchoring for boots, makes the player sink faster in water
- Fixed an error with the logic of Bloodlust and slightly nerfed it - previously level 2 would incorrectly give 10 seconds of strength rather than 7, and it has been lowered to 6. Level 1 remains at 4 seconds.
- Minor tweaks, fixes & improvements