The script now uses the same library files used by mass-multiboot.py, but is a
bit more interactive to the user than mass-multiboot.py.

mass-multiboot.py is intended to be used from the server directly to update
cards in a crate.

multiboot.py is intended to be used locally by a user, either to update a single
card, or to debug which gateware versions are loaded on the card's flash.