Visualiser hopefully now ready to use jsons.

I've changed the visualiser to use jsons, I'm still a little iffy on the
format they'll be in, but jsons are nice enough that it won't be much
effort to correct if bits are wrong.
I've added a step which shows where values are missing and a step which
highlights data marked as wrong, but haven't decided on a criteria by
which data is decided as wrong (currently marks all errors as wrong for
display purposes).
Tidied up the interface a little.