Start using Smex

For some reason, I had installed it, but wasn't using it...
Make functions autoload, and deal with files
Improve Magit config, move it to the right place
Use a better version of delete-file-and-buffer
Make both smex commands available

I was confused that the default configuration seems to suggest setting
both smex and smex-major-mode-commands to M-x; and it seems a lot of
people just copy that without thinking about it. I don't know if I'll
use C-x M-x much, because it kind of sucks, but it certainly doesn't
deserve to be the default.
Switch to a working ido + recentf function