Fix world preparation status output. Fixes BUKKIT-4407
Send event-defined MOTD/maxplayers. Fixes BUKKIT-4409

Also, revert to previous CraftBukkit functionality
Update client on cancelled leash. Fixes BUKKIT-4395
Update client on cancelled entity naming. Fixes BUKKIT-4396
Added EntityHorse for diff visibility.
Fix donkey/mule dupe exploit.
Minecraft spec has changed and we're required to follow. We now build with Java 6.
Fix scaling for player health. Fixes BUKKIT-4431
Properly clear attributes on remove and death. Fixes BUKKIT-4416
Improve maps.yml. Fixes BUKKIT-4419

Additionally fixed Minecart's interface to map INVALID methods.