Implement SpawnReason.NETHER_PORTAL and DISPENSE_EGG. Fixes BUKKIT-3148

Previously any entities spawned through dispensers (monster eggs) or
by nether portals were given the incorrect SpawnReason of SPAWNER_EGG.
This made it impossible to distinguish what exactly happened in regards
to the creature being spawned.

A method in ItemMonsterEgg has been added to further fine tune reasons
for spawning creatures. This permits the DISPENSE_EGG reason to be used
correctly and accuratly as well as the NETHER_PORTAL reason due to how
BlockPortal spawns the mobs.

The redirected method, a(World, int, double, double, double), is still
called by the ItemMonsterEgg itself and therefore uses the default reason
of SPAWNER_EGG. This does not change previous behaviour.
Update clients when ItemFrame direction is set. Fixes BUKKIT-3371

Hanging entities are placed into the entity tracker and updates are sent
out to clients for the initial placement. Thereafter data watchers are
configured to monitor the item inside the frame. However, if the
direction the ItemFrame facing changes the entity tracker will not send
out updates.

This commit removes and recreates the ItemFrame entity in the same way
that was already done for Painting entities. This causes clients to
be updated appropriately.
[Bleeding] Correctly enchant books. Fixes BUKKIT-5302

Books can now recieve more than one enchantment.  As such, breaking out of
the loop after only 1 enchantment is applied is not the correct behavior.

This commit also reworks some of the logic surrounding the application of
enchantments to the item. By checking if the event doesn't add any
enchantments rather than if the original enchantments list is empty, the
application code is only reached if enchantments are applied, rendering
the "applied" boolean no longer necessary. The ItemStack's Item should only
be set once, so it is now set outside of the loop based upon whether or not
"flag" is true (with "flag" being whether or not the ItemStack's Item is a
book).
Implement banning API. Adds BUKKIT-3535

Previously no implementation existed to access various additional
information fields regarding bans. This implementation expands on the
information outlined in the sister Bukkit commit to provide access to
the Minecraft implementation of the ban system.

This implementation of the banning API contains 2 new classes which
provide access to the internal workings of the built-in banning
system within Minecraft.

The CraftBanEntry class simply supports the representation of an internal
Minecraft BanEntry object. The data that may be modified within this new
object must be manually saved to the list contained within the
CraftBanEntry using it's save() method.

The CraftBanList class supports the representation of an internal
Minecraft BanList object through proxy methods. These methods do
validation on the passed objects where needed to ensure safe input to the
backed Minecraft objects.

These changes additionally re-route the existing banning API to the newer,
more detailed, system. Functionality prior to this change still behaves
as documented by the contract defined by the methods changed.
[Bleeding] Implement Mojang command fallback system. Adds BUKKIT-5385
Match old alias behavior when migrating.

Previously the alias system would pass all arguments from the alias
to its command(s) implicitly. The new system requires arguments to be
explicitly passed so server owners can have more control over where and
how they are passed. To ensure this isn't a breaking change during the
migration from bukkit.yml to commands.yml we now add the $1- argument
to the alias commands to match the previous behavior.
Readd BlockPlaceEvent for half slab to full block. Fixes BUKKIT-5390
Add method to forget callbacks in AsynchronousExecutor