version 2.6 BETA including "personality test" feature

Signed-off-by: Joseph Rézeau <moodle@rezeau.org>
Merge branch 'MOODLE_26_STABLE' of github.com:remotelearner/moodle-mod_questionnaire into MOODLE_26_STABLE
added relevant links to the online help for new Personality Test feature (2.6)

Signed-off-by: Joseph Rézeau <moodle@rezeau.org>
Fixed missing checks on required and name for YES/NO questions to include in Feedback sections!

Signed-off-by: Joseph Rézeau <moodle@rezeau.org>
CONTRIB-4778 :: In Conditional branching questionnaire, back navigation deletes previous answers.
CONTRIB-4779 :: Do not prevent from navigating to previous page when required questions on page are left unanswered.

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