Bukkit

- Add World Drop Filter (Define which worlds a head can drop in)
- Add Weather Drop Filter (Define what weather a head can drop in - Rain, snow, thunder, or clear!)
- Add looting / fortune enchantment functionality for head drops
- Add configurable update notification levels - Define whether to get updates for patches, minor updates, or major overhauls.
- Add notifyupdates permission
- Fix a bug where player heads wouldn't consistently stack between reboots and logouts
- Player heads placed on 2.1.0 will retain their skin even when broken
- New heads!

    - Tea
    - Coffee
    - Birch Wooden Crate
    - Spruce Wooden Crate
    - Jungle Wooden Crate
    - Acacia Wooden Crate
    - Dark Oak Wooden Crate
    - Crimson Wooden Crate
    - Warped Wooden Crate
    - Piglin Head
    - Zombified Piglin Head
    - Strider Head
    - Mini Nether Wart Block
    - Mini Warped Wart Block