MDL-43369 : quiz statistics - average across attempts where item seen

and not across all attempts for subqs.
MDL-41384 upgrade: make sure to re-read $SITE from DB when course table is altered
MDL-41384 course: do not show debugging message if $COURSE contains format options

before showing debugging message make sure that field exists in database and not only in the object
Merge branch 'MDL-43369-26' of git://github.com/jamiepratt/moodle into MOODLE_26_STABLE
MDL-43805 assign: Prevent behat fail on ci - editpdf is not available there

Ghostscript is not setup on the ci servers, so the editpdf feature will be automatically
disabled. This means that I cannot click on "Hide Annotate PDF".
Merge branch 'wip-MDL-41384-m26' of git://github.com/marinaglancy/moodle into MOODLE_26_STABLE
Merge branch 'MDL-43911-26' of git://github.com/andrewnicols/moodle into MOODLE_26_STABLE
MDL-42339 - removed double formatting for set_title() and set_heading()
Merge branch 'MDL-42339_m26' of git://github.com/rwijaya/moodle into MOODLE_26_STABLE
MDL-43936 questions: fix my lame spelling in upgrade.txt.

Thanks to Mark Nelson for the suggested improvements.
Merge branch 'MDL-43936_26' of git://github.com/timhunt/moodle into MOODLE_26_STABLE
MDL-43926 files: Unit tests cannot assume id values.
weekly release 2.6.1+
MDL-43992 Javascript: Remove <return> key listener for confirmation

The listener was previously confirming, even when the cancel or 'No'
buttons were selected. However, having the default action as 'Confirm'
seems dangerous in this situation, so removing this option entirely.