File progress form element

A form element will display a spinner for file progress. It will need to be hidden (via CSS so it doesn't appear for non-js users), and will be placed above the file browser.

A wrapper will be placed around the 'Add file' submit button, and will have behavior attached to hide the browser and display the spinner element. The AHAH $output from the submission will appear in that section, and will include a Checkmark, followed by any system messages/errors. (Obviously, we should have a big red X if it's not successful).