[Bleeding] Simplify command handling.

Instead of duplicating code to handle two pools of commands
we can instead just add the fallback commands after all
plugin commands are loaded and achieve the same effect. We
also now always register the direct address of a command
to ensure it is always possible to access it.

In addition, aliases can be determined by whether or not
the command label of the command matches the command address,
thereby rendering the aliases HashSet redundant.
[Bleeding] Improve alias system.

Adds a large expansion of the aliases system. Aliases can now take arguments,
reorder their arguments, and only pass certain arguments to certain commands.
New syntax added to the aliases are $1 for optional arguments, $$1 for
required arguments, $1- for optionally using all the arguments from the
specified position onward, and $$1- to do the same thing but require at least
the specified position exist. These exist for numbers 1 through 9. You are
able to pass arguments to one command of a multiple command argument and not
others. You can also use the argument as a prefix and/or suffix. A raw $ can
be represented in the arguments by using \$.

Examples:

aliases:
# Usage: /testobjective score_deaths 1 5
testobjective:
- "testfor @p[$$1=$$3,$$1_min=$$2]"

# Usage: /ban Amaranthus Because reasons
ban:
- ban $$1 $2-
- say Banned $$1

# Usage: /icanhasbukkit
icanhasbukkit:
- version

# Usage: /icanhasplugin HomeBukkit
icanhasplugin:
- version $$1

One change from the previous aliases system is that commands are no longer
passed all arguments implicitly. You must explicitly pass the arguments
you want to pass to the command.