MDL-27508 workshop: improved getting of potential authors and reviewers
MDL-27508 workshop: improved getting of potential authors and reviewers

This patch reimplements get_potential_authors() and get_potential_reviewers()
so that get_enrolled_sql() is used instead of get_users_by_capability().
This excludes non-enrolled users (or users with suspended enrolment)
from the list of potential users.

The patch also extends the returned user structure. Objects in the
returned collection are now suitable for user_picture renderer.

dilawar/moodle