Guhllar Notes

Adds three denomination of note for 1, 64, and 4096 Guhllars.
Dropped note items are invulnerable and don't despawn (aside from being thrown in the void).
All players can use /signnote to sign a held stack of notes.
Signed notes can only be unsigned by the signer or a moderator using /signnote erase.
Notes can be converted between denominations by right-clicking while holding, or by shift+right-clicking in the inventory.
Notes are uncraftable and are means to be managed by an admin.