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 
:+1:  Also as part of that conversation, we noted that if a user *does* need to make changes to a private study (which will inevitably happen), it will be placed back in sandboxed mode, and made to be consistent with the constraints of that mode (i.e., if it was shared, it will be unshared, and users with whom the study was shared will be notified of the change)