CYB-216 Student activity before using DC app should still create student

* If a canvas_user_id appears in the stream and does not have a Student record, one is created from data retrieved with a Canvas API call
* API key for the app will have to have account level permissions; the /profile call will require a higher permission than just 'Teacher'.

[CYB-216 Student activity before using DC app should still create student](https://jira.ets.berkeley.edu/jira/browse/CYB-216)