Use study status properly

This blocks the attachment of raw data to the study until after the study metadata is approved. It also adds two buttons for admins to approve a study and to make a study public.

This finishes #476 
Personally, I don't like this programming paradigm.  If we need to send post data, why not use [jQuery's post function](http://api.jquery.com/jquery.post/)?  Doing so would also help reduce the chaos in the `StudyDescriptionHandler`, since each call to `post` could (if we wanted) hit against its own AJAX handler and update the current rendering of the study_description.html without needing to fully refresh the page (which is a better UX)