More fields on course model on email settings

My idea is to include setup for the following functionalities after course creation:
- allow email cc setting
- allow reply-to in email header

for receiving or not, receiver including TAs or not, for each kind of emails, including registration, participation approval, students' question on human graded question after grades release and TAs' question about grading of specific session. The last two need to be done by extending page api.