Move aliases to their respective cogs

[MarkKoz]

I think it's easier to maintain aliases if they are located near the actual commands. Furthermore, creating separate functions for aliases feels redundant and harder to maintain (particularly the parameters and their type annotations). I wonder if it's possible to create a decorator for commands which can add an alias for a command. Perhaps the command resolution of discord.py can be manipulated rather than having to create "dummy" commands for aliases (this may prove to be complicated for subcommands/groups particularly).

The point of this issue right now is to have some discussion on what a good design would be and some ideas for implementations.

[MarkKoz]

This is getting stale. I will try to explore the decorator idea myself soon, as I like the sound of the idea on the surface and no one else has said otherwise so far.