MDL-40515: report_log: List activities in optgroups

Prevents users from generating reports on invalid values

Change-Id: If358fa06c8dadd33bb2875ea54ab4bce97b16aff
MDL-22669 course: Display section number for orphaned activities
MDL-38664 Lesson mod: fixed re-attempt unseen page
MDL-38664 Lesson mod: code improvement for lesson attemps
MDL-36818 cas: improve SSL validation
MDL-42347 course: Added behat test for deleting a course
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-42282 Behat: Automated test for MDLQA-509

MDLQA-509: A teacher can prevent students from accessing an activity
between specified dates
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-42489 backup: use correct exception class in automated backups
MDL-42283 Behat: Automated MDLQA-1777

MDLQA-1777: A teacher can set grade conditions to restrict availability of a section
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-42285 Behat: Automate MDLQA-93 - A teacher can delete questions from the question bank
MDL-42491 libraries: add exception for IE11 (and hopefully later versions)
MDL-42533 conditionlib: Field name is translated for students
MDL-42538 behat: Fixing wrong number of users