Make HopperMinecart implement InventoryHolder. Adds BUKKIT-3796
Add InventoryPickupItemEvent. Adds BUKKIT-3798
Add block or entity causes to BlockIgniteEvent. Addresses BUKKIT-3609, BUKKIT-3656, BUKKIT-3657
Add per-player Weather API. Adds BUKKIT-812
Add dummy /testfor command in Bukkit. Addresses BUKKIT-3813

This command only functions in command blocks so the bukkit command for it
simply spits out an error message.