Allow doing bot commands by messaging bot

[cpdt]

Courtesy of @byronmejia, hopefully pretty self-explanatory... when a user gets the welcome message as a PM, it makes sense that they'd be able to respond directly to that to join roles and things.

[byronmejia]

!role add qut

[byronmejia]

Ahh heck, this isn't discord.

[jabelone]

That's a cool idea! Definitely something we can do.