Don't check unload queue before ticking things anymore.

In commits 71a238ee and c8591397 we added checks while ticking to ensure
we never ticked anything in a chunk meant to be unloaded. We did this to
prevent these chunks being removed from the unload queue and leaked.
However, this causes a ridiculously large number of lookups on the queue
for a somewhat rare occurance. We also now have the chunk GC which will
take care of these leaked chunks when they do happen. With this in mind
we now remove these checks which removes almost all uses of the
LongHashSet backing the unload queue.
Avoid checking for loaded chunks for lighting and entity ticking.

When a chunk is loaded the server tries to ensure it has its initial light
calculations done before sending it to the player. When ticking entities
the server tries to ensure the entity does not walk into an unloaded chunk.
To accomplish these the server checks a one chunk radius around the chunk
to be lit or a two chunk radius around the chunk the entity is in. These
lookups happen every tick even though their result is unlikely to change
that often. To reduce the cost of these checks we replace them with a
system to keep track of what neighbor chunks a chunk has loaded and update
it when chunks load or unload which is a much less frequent action. On a
server with ten players this change removes about 100,000 calls a tick to
LongObjectHashMap's containsKey method.
POM Changes
mc-dev imports
Skeleton API Implementations
Obfuscation Helpers
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
Improved Timings System

Tracks nearly every point of minecraft internals and plugin events to give a good quick overview on what is causing TPS loss.
Fix Mob Spawning Relative to View Distance
Handle Null Tile Entities
Entity Activation Range

This feature gives 3 new configurable ranges that if an entity of the matching type is outside of this radius of any player, will tick at 5% of its normal rate.

This will drastically cut down on tick timings for entities that are not in range of a user to actually be "used".
This change can have dramatic impact on gameplay if configured too low. Balance according to your servers desired gameplay.
Metrics