Fix: dashboard course sorting
access_resource_library link
add download certificate pdf function
Modify: sort dashboard courses by date
 Modify: sort dashboard courses by date desc
Modify: people search course dorpdrown: sort item by course number
Merge branch 'lvzh' into www0
Merge branch 'victor' into www0
Merge branch 'star' into www0
Add couse discussion information page, modify the portfolio - My coursework \ My discussions static pages