[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 fallback version 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] Blacklist certain plugin names
[Bleeding] Improve alias system.
[Bleeding] Blacklist ":" in command names.