Finished refactor of EntityItem death drops.

This completes the refactor which started in commit
MinecraftPortCentral/Cauldron@aadc2f319f7db308043e4072eb93114604593697

* Fixed mystcraft age trapping.
* Fixed bukkit KillCommand ignoring LivingDeathEvent.
* Moved horse inventory dropping which was fixed in commit
Bukkit/CraftBukkit@fb58cc92375d85bfe7a3dc8671c70d1a4e308e3c