Start ripping out interface segments ...

... to make way for visualisation segments. I never really liked the way
the old createInterface mechanism worked, and it required a lot of code
that seemed to nearly duplicate what the browser does already. Have also
been recently impressed by @enjalot's tributary and am heading towards
integrating that, or something like it. This is all made harder, as
always, by the unspeakably wretched cursor code. But I'm trying my best
to ignore that at the moment.
Pull cursor code out of viewmodels.

An attempt to make the code a bit more readable. I don't really want to
do a whole cursor re-write now, but it would be good to be able to see
the structure of the viewmodels more clearly.
Rip out all of the visualisation segment stuff.

Decide that the code segment is all that's really needed. Or at least,
am going to try that initially.
Basic live evaluation.
Initial stab at live evaluation with visual output

Very clunky at the moment, but the essence is there. Looks quite
promising (with a lot of imagination!).
Add Inlet.

Need to clarify Inlet licence and Color.Picker.Classic licence.
Very basic UI for live and visual modes.
Persist live and output modes.
Try moving visual output and code side-by-side.

Breaks the rest of the layout, but looks pretty sweet! Need to clean up
all of the layout stuff anyway.
Individual visibility state for browser and vis.
Use to JSHint to detect errors before evaluation.

This makes the visual output a bit more stable in live editing mode. The
idea was taken from @enjalot's Tributary.
Object browser visibility toggle control.
Code segment glow for error feedback.
Improve code segment settings UI.

Settings now drop out of a cute little menu.
Move visual output alongside code.

And improve styling all-round. Clean up the CSS a bit, but it still
needs more sorting.
More UI feedback on live evaluation.
Allow expressions to pass lint.

In a notebook, many things will just be expressions.
Fix bug where code editor would become corrupt.

When showing or hiding the output pane, the editor would not reflow its
contents.
Improve error reporting on manual evaluation.
Improve error text output when there are no hints.