Add autodocs of modulestores
Fixes Carlos's bug
Fixes ../courseware/Peer_Grading_Panel/peergrading:L12P5_grading/ reported bug
Serialize course_key at last possible code junction
Merge pull request #3791 from edx/dhm/bug_open_ended_notifications

Dhm/bug open ended notifications
Merge pull request #3781 from cpennington/opaque-keys-more-docs

Add autodocs of modulestores
Merge pull request #3787 from edx/dhm/bug_mktg_url

marketing url too many slashes
Fix student progress @sarina bug