- give the preview div an id, use that to look it up instead of dancing around in the DOM

- I'm starting to vaguely understand js variable scope and closures.  Long way to go though :)

- architecturally slightly questionable: the preview ajax calls goes to an LMS view instead of an input type specific one.  This needs to be fixed during the grand capa re-org, but there isn't time to do it right now.
- also, I kind of like having a generic turn-a-formula-into-a-preview service available