Only display certificates for courses that a teacher is teaching

[wigglemuff]

Here's what the user says:

Ok. The basic idea is that I'm trying to see if there is a way to make the "Certificates" area within the dashboard behave like the "Courses" area.

For example, a teacher can only see the course that they are assigned to. But in the certificates area they see EVERY certificate.

I have an example of what I'm seeing here: http://americanmedicalcompliance.com/example.jpg

tl;dr They want - A teacher can only see certificates of the course they're assigned to (and not all the certificates).

Ticket: https://woothemes.zendesk.com/agent/tickets/1035844

[wigglemuff]

I think I don't have access to add labels in certificates repo. If I could, I would add the enhancement label to this one!