MDL-40515: report_log: List activities in optgroups
MDL-22669 course: Display section number for orphaned activities
MDL-36818 cas: improve SSL validation
MDL-38734: Automated backup failure causing all course to fail
MDL-42111 TinyMCE media preview: fix video preview display for TinyMCE media.

Effected themes: boxxie, clean, brick, formal_white and splash.
MDL-38664 Lesson mod: fixed re-attempt unseen page
MDL-38664 Lesson mod: code improvement for lesson re-attempt page
MDL-42453 theme_base: Fixed Error in base/style/admin.css that breaks CSS validator.
MDL-34612 Restore: Gracefully handle empty section title while restoring
MDL-34612 Restore: Gracefully handle empty file contenthash while restoring
MDL-42465 mod_chat: instantiated message object before declaring properties
MDL-42489 backup: use correct exception class in automated backups
MDL-42494 Fix workshop coding exception if all assessments have zero weight

If all assessments for the given submission have zero weight, the grading
evaluation plugin "Comparison with the best assessment" is unable to decide on
the average assessment as it ignores those with zero weight. In such rare case,
it makes sense to set the grading grade to null and prevent the coding
exception.
MDL-34654 Glossary: ampersand breaks auto-linking
MDL-42491 libraries: add exception for IE11 (and hopefully later versions)
MDL-42533 conditionlib: Field name is translated for students
MDL-42542 portfolio: Fix handlerfile in portfolio event handler
MDL-42270 course: Section name too big message.
MDL-42548 quiz review: don't show grade for non-finished attempts.

Now we show the attempt state separately, so there is no need to show
Grade: Attempt still in progress - especially since we were showing that
for abandoned and overdue attempts which is just wrong.
MDL-42551 timezone info: updated to 2013h