Add StatisticManager.java for diff visibility.
[Bleeding] Fix Achievements and Statistics API. Fixes BUKKIT-5305
[Bleeding] Implement methods for /achievement command. Addresses BUKKIT-4932
[Bleeding] Check that vanilla recipes actually exist. Fixes BUKKIT-5277

When falling back to vanilla recipes in the iteration of recipes,
a check is necessary to ensure that vanilla recipes are present.
RecipeIterator has been modified to account for the multi-map setup.
[Bleeding] Account for null in EntityDamageEvent handling. Fixes BUKKIT-5317

Damage caused by explosions will return null for the event as of
6588d6f72bbca74bf150de65593ac575b846111b. As such, a null check is
now necessary when handling non-living entity damage events.
 [Bleeding] Properly handle EntityBreakDoor event canceling. Fixes BUKKIT-5318

The method being called was renamed during the 1.4.2 update process
but the function call was not replaced accordingly, leading to a
missed diff from 314051580a0a8e4745d3a539f232b552916eb302.
Implement API for ServerListPingEvent. Adds BUKKIT-5121, BUKKIT-2465
POM Changes
mc-dev imports
Skeleton API Implementations
Spigot Configuration
Better Chunk Tick Selection
Crop Growth Rates
More Efficient Chunk Save Queue
Merge tweaks and configuration

This allows the merging of Experience orbs, as well as the configuration of the merge radius of items. Additionally it refactors the merge algorithm to be a better experience for players.
LongHash Tweaks
Async Operation Catching

Catch and throw an exception when a potentially unsafe operation occurs on a thread other than the main server thread.
View Distance

This commit allows the user to select per world view distances, and view distances below 3. Be wary of the issues selecting a view distance of 1 or 2 may cause!
Compressed Nibble Arrays

Implement 'lightening' of NibbleArrays - only allocate
 buffers when non-trivial value Saving from 40-45% of memory use by chunk
 section data.

Finish up NibbleArray lightening work - use for Snapshots, reduce copies

Fix nibble handling with NBT - arrays aren't copied by NBTByteArray
Sync Free Chunk Reference Cache