Add chart -u to set base url
Generate and show configs when url is set
Sketch out how data dimensions could be guessed

This particular code is not long for the world.  It is better to do this work
server-side than client-side.
Make server guess config if none is specified
Allow matching strings to natural types

This makes sense because data sent to the server is deserialized - meaning it
might be the value or it could be a string representation of the value.  This
provides a sensible and consistent guessing mechanism that treats strings as
the values they look like.  If the user ever want, say "1" to mean the string
"1" then they can manually specify the dimensions as configs.
Make config guessing the same on the client as the server
Remove guessing of configs client-side

This is done server-side.