Refactor minigrace js output into minigrace.js.
Remove interactive and util modules from js.
Fix missing include of StandardPrelude in js.
Made MiniGrace object.
Decouple mode, define minigrace in minigrace.js.
Decouple modname.
Decouple JS stdout/in/err from HTML elements

Previously, the various read and write methods directly accessed the DOM
to manipulate the values of the actual textareas on the page. Now,
abstract that manipulation away behind functions so that the compiler
can be included in different pages.
Fix not outputting generated code.