Add fedup.util.kernelver()

This function will parse the version number out of a vmlinuz kernel
image.

..I actually can't remember why I needed this right now, but I'm sure
I'll be pretty happy about it when I remember why I needed to write it.
Move argument parsting to fedup.commandline

This lets us share the commandline parsing between the GUI frontend (or
perhaps frontends) and the CLI. Whee!
Use fedup.commandline to parse commandline args

Yep, we parse some commandline args now, so people can use --instrepo
and junk if they feel like it. Not that it's wired up or anything.
Update TODO

Having talked to a resident mdraid expert, it turns out that migrating
device names isn't gonna be enough to fix /dev/mdX problems. So drop
that idea.

Plus, other updates. WHAT FUN.