[API] Include course "status" in the output of the "courses" API endpoint

[patdura]

The courses API endpoint does not return the "status" of a course. 

This makes it difficult to repair course settings via the SIS Import for courses since course status is a required field and there is no way to get the current course status via the UI or via the API.

Ideally, the "status" should be returned by the API call to get a single course:

GET /api/v1/accounts/:account_id/courses/:id

The valid values for course status (according to the SIS import documentation) are: active, deleted, completed, published