Update to 3.1.2

Upstream changes:
3.1.2

Highlights

    MDL-37250 - Lessons: save students attempts if they timeout
    MDL-54977 - Fixed bug with navigation tree not working in some cases
    MDL-50586 - Warn teachers about removing level 0 in rubrics as it leads to unexpected grades.
    MDL-41174 - Update the calendar event when inline changing activity name or duplicating activity
    MDL-33741 - Allow teacher to access course files in hidden categories using Server files repository in filepicker
    MDL-55333 - Fixed error when trying to view/export feedback responses with over 60 questions using mariadb/mysql

Security issues

    MSA-16-0022 Web service tokens should be invalidated when the user password is changed or forced to be changed

Fixes and improvements

    MDL-55312 - Bugfix: Load timeout for modules: core/first occurs after purge caches
    MDL-55229 - Bugfix: Meta Enrolment - Search for course produces error
    MDL-55707 - Bugfix: Possible to get in "recalculating grades" infinite loop
    MDL-55292 - Include tideways profiler along with xhprof for PHP7 profiling
    MDL-54892 - Uninstall scheduled tasks when plugin is uninstalled
    MDL-22183 - Prevent stats from running later and later - use scheduled task time only
    MDL-47371 - Bugfix: The character & is displayed as " & amp ; " in book module
    MDL-52544 - Resolved problems of Oracle driver in PHP7 environment
    MDL-55246 - Bugfix: Unoconv fails on files with spaces in the name.
    MDL-51078 - Add "All changes" option to the Action selector in report_log (was present in 2.6 and removed in 2.7+)
    MDL-52105 - Remove CAP_PROHIBIT in manager role for capability 'enrol/self:holdkey'
    MDL-54847 - Allow students to insert HTML audio and video tags
    MDL-55273 - Default setting for cookiesecure should be on
    MDL-55520 - Assignment module no longer resets max grade to 100 during module editing
    MDL-55245 - Attempting to select text in PDF annotation comments drags the comment box

(wen)