Add EntityEquipment API. Adds BUKKIT-3103

Adds:
- Getting/Setting equipment
- getting/setting drop rates
- getting/setting ability to pick up items
-- As an added feature, players with this flag start off with a canceled PlayerPickupItemEvent
Missed a rename
Players should be able to pick up items by default. Fixes BUKKIT-3143

As an added feature, players defaulted to being able to not pick up items if the flag was false. However, since minecraft doesn't normally use the flag on players, the flag was always false.
Fix players not being able to pickup items due to default values.

The old flag for picking up loot was default to false, making existing players not able to pickup items. We now use this flag for Players, which gives us the problem we had in 48b46f83.

To fix this, we add an incremental flag that will be cross-examined to check if the data was saved before or after the flag level was introduced.

Addresses BUKKIT-3143
Don't run mob pickup code on players. Fixes BUKKIT-3150

When a player has canPickUpLoot set to true the code for mob pickup is
triggerd which does not know how to deal with player inventory. Since
players have their own logic for picking up items we simply disable this
code for them.
Add utility class AsynchronousExecutor

This class is a general purpose task execution system, that uses stages
to separate processing blocks for asynchronous and synchronous
executions.
Add RegionFile from mc-dev for diff visibility
Load chunks asynchronously for players.

When a player triggers a chunk load via walking around or teleporting there
is no need to stop everything and get this chunk on the main thread. The
client is used to having to wait some time for this chunk and the server
doesn't immediately do anything with it except send it to the player. At
the same time chunk loading is the last major source of file IO that still
runs on the main thread.

These two facts make it possible to offload chunks loaded for this reason
to another thread. However, not all parts of chunk loading can happen off
the main thread. For this we use the new AsynchronousExecutor system to
split chunk loading in to three pieces. The first is loading data from
disk, decompressing it, and parsing it in to an NBT structure.  The second
piece is creating entities and tile entities in the chunk and adding them
to the world, this is still done on the main thread. The third piece is
informing everyone who requested a chunk load that the load is finished.
For this we register callbacks and then run them on the main thread once
the previous two stages are finished.

There are still cases where a chunk is needed immediately and these will
still trigger chunk loading entirely on the main thread. The most obvious
case is plugins using the API to request a chunk load. We also must load
the chunk immediately when something in the world tries to access it. In
these cases we ignore any possibly pending or in progress chunk loading
that is happening asynchronously as we will have the chunk loaded by the
time they are finished.

The hope is that overall this system will result in less CPU time and
pauses due to blocking file IO on the main thread thus giving more
consistent performance. Testing so far has shown that this also speeds up
chunk loading client side although some of this is likely to be because
we are sending less chunks at once for the client to process.

Thanks for @ammaraskar for help with the implementation of this feature.
Fix EntityEquipment positions being reversed. Fixes BUKKIT-3157
Add isRecord and new material method tests.

Cleaned up all of the CraftBukkit tests, including moving some tests
from MaterialTest to PerMaterialTest.
ItemStack.asBukkitStack(null) should return Air. Fixes BUKKIT-3170
Implement ItemFactory and ItemMeta values. Adds BUKKIT-15
Merge branch 'master' of git://github.com/Bukkit/CraftBukkit.git