CONTRIB-4785 :: Make List of individual anonymous responses available to the teacher (again)

Signed-off-by: Joseph Rézeau <moodle@rezeau.org>
CONTRIB-4788 :: removed the GROUP BY instruction which caused an error in Postgres and was un-needed.

Signed-off-by: Joseph Rézeau <moodle@rezeau.org>
CONTRIB-4789 :: Questions have required flag when they are not required

Signed-off-by: Joseph Rézeau <moodle@rezeau.org>
CONTRIB-4787 :: email non-respondents in an anonymous questionnaire

Signed-off-by: Joseph Rézeau <moodle@rezeau.org>
CONTRIB-4800 :: Enable teachers to preview template or public questionnaires located in courses where they are not enrolled

Signed-off-by: Joseph Rézeau <moodle@rezeau.org>