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 
Yep -- I think we're all in agreement.  This function is too big.  IMHO, it should be broken into several handlers, and study_description.html should be updated to match.  @squirrelo, can you create an issue?  Also note that study_handlers.html uses ORM objects, some of which are passed into the `render` call, and some of which are instantiated in the template itself.