Set last accessed variables after grabbing chunk. Fixes BUKKIT-1033

This fix changes the 'state' of the last accessed variables to be more
accurate. Changing the coordinates of the last accessed chunk should
never precede actually setting the last accessed chunk, as loading a
chunk may at some point call back to getChunkAt with a new set of
coordinates before the chunk has actually been loaded. The coordinates
would have been set, but the actual chunk would not. With no check for
accuracy, this causes fringe case issues such as null block states.

Big thanks to @V10lator for finding where the root of the problem was
occurring.
Replace LongObjectHashMap with a more efficient implementation

After further testing it appears that while the original LongHashtable
has issues with object creation churn and is severly slower than even
java.util.HashMap in general case benchmarks it is in fact very efficient
for our use case.

With this in mind I wrote a replacement LongObjectHashMap modeled after
LongHashtable. Unlike the original implementation this one does not use
Entry objects for storage so does not have the same object creation churn.
It also uses a 2D array instead of a 3D one and does not use a cache as
benchmarking shows this is more efficient. The "bucket size" was chosen
based on benchmarking performance of the HashMap with contents that would
be plausible for a 200+ player server. This means it uses a little extra
memory for smaller servers but almost always uses less than the normal
java.util.HashMap.

To make up for the original LongHashtable being a poor choice for generic
datasets I added a mixer to the new implementation based on code from
MurmurHash. While this has no noticable effect positive or negative with
our normal use of chunk coordinates it makes the HashMap perform just as
well with nearly any kind of dataset.

After these changes ChunkProviderServer.isChunkLoaded() goes from using
20% CPU time while sampling to not even showing up after 45 minutes of
sampling due to the CPU usage being too low to be noticed.
Fix crash from console-commands throwing exception. Fixes BUKKIT-2479

When 1.3.1 was released, a try-catch block was removed from the tick
loop that called the method in NMS to handle commands. This restores a
try-catch to prevent the console from crashing the server.
Bulk pending cleanup.
Fix crash from console-commands throwing exception. Fixes BUKKIT-2479

When 1.3.1 was released, a try-catch block was removed from the tick
loop that called the method in NMS to handle commands. This restores a
try-catch to prevent the console from crashing the server.
Bulk pending cleanup.
Spigot changes.
Reduce excessively high frequenccy chunk lookups in core entity logic routines
Avoid spawn checks on empty worlds, and exceeding world mob type limits

Check for player count on world, versus whole server - avoids wasteful
checks of worlds that will have no viable chunks for spawning.

Use difference between mob limit and mob count to avoid having spawn
cycle potentially spawn many more mobs than limit allows (can happen on
large servers with lots of players near favorable spawn locations, esp
squids and animals)
(experimental) have squids use same in-water test as other mobs (vs expensive call)
(experimental) Don't limit compression thread queue: can block server thread
(experimental) fix for shutdown hang on user disconnect processing
Add NetworkReaderThread from mc-dev for diff visibility
(experimental) Avoid interrupting already interrupted read/write network threads
Add log-commands setting just for @kainzo
Switch to constant time structure for chunk save queue for ChunkRegionLoader
Commented out debug code but left in bandaid for broken entities.
Removing Cosmetic goals from animals