Use it in the updater and all the importer tools. Only place it's not
used yet is parking_mapper and the in-game updater. [rebuild]
Also make the RunCommand state understand the control code for erasing
the current line. It... sort of works.
widgetry, geom, and abstutil may wind up on crates.io in some form to
let other projects use widgetry. abstio has A/B Street-specific tricks
for reading data on native/web. Note widgetry still depends on abstio,
will figure out how to clean that up next.
