Form elements

[pigworker]

Pandoc does allow us to write form elements, but only in that we're allowed to write things like

`<input type=text name="foo">`{=html}

`<input type=submit>`{=html}

I think we should write less and achieve more. We need some way to signal the existence of form fields to the shonkier runtime, so that field value requests can be handled. We should also be able to attach a preprocessor to a form field which eats text and emits a value or aborts; field value requests should yield the output of the preprocessor.
(One day, when our language is typed, the preprocessor will be type directed.)

We could have something like

`'foo`{.in type=text size=12}

to signal a form field bound to the atom 'foo. To access this field, invoke

'field('foo)

We might, further, write

`'bar <- parser`{.in type=text size=100}

where parser is an expression yielding a function which eats string literals.

[pigworker]

This is alive. We need to wire this up to some sort of ontological model. We also need to get some more active field manipulation happening in the javascript runtime.