Added cron driven auto-pull of excerpt from certificates_generated
certificate. The process adds the hash anon_screen_name to the integer
user_id column. The table is loaded into EdxPrivate.UserGrade, b/c
it includes the screen names (however, see below).

Added cron driven auto-pull of courseware_studentmodule excerpt.
Before being loaded into the new Edx.ActivityGrade table, the
anon_screen_name is added, and the module_id is replaced by its resolution to a human readable string.

Added a new view: Demographics, which pulls some parts of the EdxPrivate.Account
information into Edx.

Stopped using MD5 from S3 eTags, b/c S3 changes its MD5 algo for files > 5GB.
They compute separate MD5s for multipart fragments, and then combine
those into one MD5. Reverted to Sef's file length method for verification.

Next: some non-Ascii chars in courseware_studentmodule that prevent
      auto-pull to finish.
Next: Performance view, which combines certificate grade with
      courseware_studentmodule activity grades.