Process block cleanup first. Fixes BUKKIT-4103

When setting a block the server sets the new block ID, calls the cleanup
on the old block, then calls the placement logic for the new block. This
would normally work correctly but we have logic to prevent errors that is
causing one here. When trying to clean up the old block we notice the block
ID has changed and try to fix things, this causes the cleanup logic to
fail. To ensure cleanup happens correctly we now do all the cleanup before
changing the block which avoids triggering the fixup code.
Only delay removing containers. Fixes BUKKIT-5238

In commit f94b7af8 I delay removing the block until after running the
block's cleanup code to avoid errors. However, this causes problems of
its own due to blocks not being written with this in mind. To avoid blocks
getting recursively removed we now only delay removing containers since
they are the only ones we had problems with to begin with.
Add failing unit test for ItemMeta-repairability
Consider repair cost when checking ItemMeta emptiness. Fixes BUKKIT-5304
[Bleeding] Implement setIdleTimeout and getIdleTimeout. Addresses BUKKIT-4932.
Implement UnsafeValues for give command. Addresses BUKKIT-5286
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
Highly Optimized Tick Loop