POM Changes
mc-dev imports
Spigot Changes
Proxy IP Filter
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.

This commit adds a flat array based cache to the LongHash(Set/Map) classes leading to excellent efficiency for servers where most activity is centered around the origin (0,0)
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!
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
Optimize packet used to unload chunks for the client

At the moment telling a client to unload a chunk involves calling the entire chunk from memory, deflating it and then sending it through the pipes even though the client ignores it and based on the bitmap simply unloads the chunk, and to add the cherry on top, this is done on the main server thread.
Alternate, sync-free-but-safe chunk reference cache
Tick loop optimization - sleep for as long as possible.
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.
Add oreobfuscator for Spigot.
Only count entities in chunks being processed for the spawn wave. Fixes mob spawn issues.
Detect, remove and warn about 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. Rewrite the Metrics system to be closer to the Bukkit version.
Watchdog Thread.
Netty

 Implement an uber efficient network engine based on the
 Java NIO framework Netty. This is basically a complete rewrite of the
 Minecraft network engine with many distinct advantages. First and foremost,
 there will no longer be the horrid, and redundant case of 2, or even at
 times, 3 threads per a connection. Instead low level select/epoll based NIO
 is used. The number of threads used for network reading and writing will
 scale automatically to the number of cores for use on your server. In most
 cases this will be around 8 threads for a 4 core server, much better than the
 up to 1000 threads that could be in use at one time with the old engine. To
 facilitate asynchronous packet sending or receiving (currently only chat), a
 thread pool of 16 threads is kept handy. == Plugin incompatibilities As a
 side effect of this change, plugins which rely on very specific
 implementation level details within Minecraft are broken. At this point in
 time, TagAPI and ProtocolLib are affected. If you are a user of ProtocolLib
 you are advised to update to the latest build, where full support is enabled.
 If you are a user of TagAPI, support has not yet been added, so you will need
 to install the updated ProtocolLib so that TagAPI may use its functions. ==
 Stability The code within this commit has been very lightly tested in
 production (300 players for approximately 24 hours), however it is not
 guaranteed to be free from all bugs. If you experence weird connection
 behaviour, reporting the bug and steps to reproduce are advised. You are also
 free to downgrade to the latest recommend build, which is guaranteed to be
 stable. == Summary This commit provides a reduction in threads, which gives
 the CPU / operating system more time to allocate to the main server threads,
 as well as various other side benefits such as chat thread pooling and a
 slight reduction in latency. This commit is licensed under the Creative
 Commons Attribution-ShareAlike 3.0 Unported license.