Staff cores

[feandrad]

Having cores for staffs allow us to have more staffs in the future, also balance the access by requiring the user to find Lapis and Gold first.

If a staff breaks, it should drop the core.

Possible cores to be added:

• 4xLapis + 4xGold Ingots in a circle: basic core
• Core + Amethyst: Replace Staff (for example)