* makes testing easier -- don't need course objects

Now looks for a status_message.json file, looks for 'global' and ${course.id} keys. Return any global message and any course-specific message, joined by <br>.

fab files need to be updated to use this new format (new filename, possibly also help manage per-course messages, or at least test for valid json)

- still needs style
- will cache for 10 seconds