Riftbone

This is a fairly big update! Thanks to FlutterCat for the additions!

• void_graves_warp_up - if this gamerule is on, graves dropped in the void get teleported to y=64 in the end and y=-64 in the other dimensions
• enable_grave_suffix - if this gamerule is off, graves just display the name of their owner, instead of "OWNERNAME's grave"
• enable_grave_opening_sound - this gamerule controls whether graves make a sound when opened
• graves now spin like items!