Fix stacking for items after setting empty meta. Fixes BUKKIT-5331

ItemStacks do not stack if one has null for a tag, while the other has an
empty tag. In CraftItemStack, if you set an item to an empty ItemMeta, it
will create an empty tag for the internal ItemStack.

This changes the setItemMeta function to check for empty meta, and then
use null for the tag instead of an empty NBTTagCompound.
Readd connection throttle
Relocate NaN check on PacketPlayInFlying.
Add BlockPressurePlateWeighted.java for diff visibility
[Bleeding] Fire interact events for Weighted Pressure Plates. Fixes BUKKIT-5053

In 1.7, Minecraft changed Weighted Pressure Plates to allow players and
entities to interact with them, rather than simply changing redstone signal
based on the number of items on the pressure plate. This commit adds calls to
PlayerInteractEvent or EntityInteractEvent for every entity that steps on the
plate.
[Bleeding] Instantiate logger earlier in CraftServer. Fixes BUKKIT-4253.

Previously, if an error occurred during CraftServer initialization before the
logger was instantiated, it would cause an NPE and the server would never
finish loading properly. By instantiating the logger before attempting to
load anything else in CraftServer, we ensure that a logger will always be
available in the case of any errors.
[Bleeding] Add support for ThrownExpBottle and Fish to launchProjectile(...). Fixes BUKKIT-1536

Previously, trying to launch a ThrownExpBottle or Fish projectile would
result in an IllegalArgumentException. This commit adds support for both
ThrownExpBottle and Fish, which means that all current projectiles are
now properly supported by this method.
[Bleeding] Re-add EntityShootBowEvent lost in e93a3eb3b4c5234e3e3936bc697d566a42d3b30e. Fixes BUKKIT-4214

In the 1.2 update for CraftBukkit, a missed diff resulted in Skeletons no longer firing an EntityShootBowEvent when they shoot an arrow.
Add methods to get and set arrow knockback. Adds BUKKIT-5103
Add setCritical and isCritical methods to CraftArrow.java. Adds BUKKIT-5113
[Bleeding] Implement ProjectileSource API. Addresses BUKKIT-1038, BUKKIT-1156
[Bleeding] Implement setCharged and getCharged for WitherSkull. Addresses BUKKIT-3060
[Bleeding] Directly set direction in EntityFireball. Fixes BUKKIT-1154

Because EntityFireball.setDirection() adds a random offset to passed
parameters, it is not appropriate for use in an API method. As such,
the values need to be directly set to remain accurate.
[Bleeding] Use correct yaw and pitch when spawning arrows. Fixes BUKKIT-3320
[Bleeding] Fix support for several entities in World.spawn(). Fixes BUKKIT-3284
[Bleeding] Store correct block type when hitting blocks. Fixes BUKKIT-5209

The block obtained and stored within the block object higher up does not
reflect the block at the location being hit, rather it is the air block
the arrow was previously in.  Thusly when the variable is used to check
if the arrow is still in the block, it fails.
Don't call duplicate interact air events. Fixes BUKKIT-5359

Previously we attempted to call interact events in cases that were missing
by modifying the arm swing logic. This, however, was too broad and started
triggering events in cases we already covered leading to duplicates. Since
the only case we can handle cleanly and the primary point of the previous
fix was fluids we now instead simply treat fluids as air for this check.
This also ensures we do not get duplicate events when the player is in a
fluid and hits a normal block, unlike the previous change.

This reverts commit 68b702f7 and replaces it with a better fix.
Allow AsynchronousExecutor.getSkipQueue() to pull tasks from the queue
Load all already generated chunks via async chunk system

Currently we use the async chunk loading system only when players trigger
chunk loading. If a chunk is loaded for any other reason it goes through
a separate codepath. This means if a player has trigged a chunk load and
before the chunk loads something else wants the same chunk we will load it
twice and throw away the second result. With this change we instead use
the sync processing feature of the AsynchronousExecutor to load the chunk
which will pull it out of the queue if it was already queued to load. This
means we only ever load a chunk once. Because chunk generation is not
thread safe we still fallback to the vanilla chunk loading system if the
chunk does not currently exist.
[Bleeding] Handle players disconnecting during respawn. Fixes BUKKIT-4327

Prior to this commit, a player disconnected during a respawn event would
remain in memory. This causes a ghosting issue of players in the slot
count and player list, as well as a reference leak.

This commit avoids re-adding the player to the player list (and world) if
they are disconnected. This ensures that the remainder of the respawn
logic is completed as well as ensuring a duplicate player is not left on
the server.

This commit also saves the player's file at the end of the method if they
have been disconnected to ensure that their next login is accurate to the
respawn event's actions. A player that was revived and disconnected will
reconnect as revived.