Profile editor: Fetch pre/post help for custom fields

I thought this would be simple (loading the pre/post help for custom fields the way the old quickform profile editor does). But the form wasn't updating when the model did, so I had to add a change handler for that. Seems like a strange shortcoming of backbone.forms that I had to do that.
But you'll be proud of me Tim that I did it the MVC way and not the much easier (for me) dom-manipulation way.