Base conversion (and alphabetizing imports)

Racpete can now translate numbers between bases! I also made things alphabetical because it was bothering me. The convert-base code is pretty ugly, I think, but I couldn't figure out a good idiomatic way to do it. Point me in the right direction and I can fix it :)
I think it would be--it seems like racket only wants to do things up to base 16, so we'd have to make our own map of numbers to characters and do everything with that. You're welcome to do it if you want