Db services

I started implementing DB services (either DataBase or Desert Bus, your pick). I made a generic subclass of Service that things can inherit from, then used that to create BidServ in its entirely. I copied the needed commands and behaviour from master branch.
Note that this branch is based on the services branch, for obvious reasons.
This stuff is not properly tested yet, and should not be considered pull-ready. But I thought I might as well start getting feedback.
This line should return `None`.  A `True` here means that it's OK to continue changing the user's nick as before.