[commands] Add bot decorators into __all__.
[commands] Add bot decorators into __all__.

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