[commands] Add Command.clean_params to have nicer params.
[commands] Add Command.clean_params to have nicer params.

These are params without the self/context parameters. Useful for
showing signature information in the help command without being
bogged down by knowing if the self/context parameters are there.
Hence it makes it easier to iterate knowing that you shouldn't care
about those two parameters.

jhgg/discord.py,Theoretical/UselessBot,rapptz/discord.py,lgkern/PriestPy,Rapptz/discord.py,imayhaveborkedit/discord.py,Harmon758/discord.py,variablehair/Eggplantato,khazhyk/discord.py,Harmon758/discord.py,mgardne8/discord.py