MDL-45763 question Random qtype should use '0' or '1' question text.

Some time ago, it when from using '0' for no-subcategories to blank.
Change to properly define '0' or '1', update old questions, and make
sure to fix newly restored questions.
MDL-45804 mod_workshop: fixed objecttable specified for the submission_reassessed event
MDL-45714 backup: Less aggressive removal of old backup dirs

The old 4 hour standard was too aggressive and can cause backup files
to be removed while they were still in use. Now the same as cron,
1 week.
MDL-45634 editor_atto: Adding type button to toolbar buttons

This prevents the browser to assume that those buttons are submit
buttons. In which case the submit action was stolen and the form
could not be submitted pressing the 'enter' key.
MDL-45789 mod_wiki: removed undefined "$this->other['itemid']" from the comments_viewed event description
MDL-45579 group: Prevent duplicate enrolment keys in course groups
MDL-45579 group: Behat tests to cover group enrolment key rules
MDL-44501 mod_data: Only attempt to export when a file exists.

The error only occurs when portfolios are enabled and there is only one field which is
a file field.
MDL-39726 backup: Move question files by context, not one at a time

Use question category contexts to send file to the file pool in bulk.
Questions are only restored in whole category chunks, so this is safe
to do.
MDL-45764 mod_lti: Fix adding General Tool

This error only occurs when a ltisource
plugin is present that implements the
get_types callback.
MDL-44309 Administration - correcting inproperly assigned column classes in environment table
MDL-45761 assign Set inline comment format properly when plugin is empty

If a plugin says it is empty, skip it for for building the inline
comment.

If not format was found in any plugins, set to FORMAT_HTML, which is
the default for feedback anyways.
MDL-20154 questions: question_delete_question should not check perms

By Moodle convention, library functions should not implement permission
checks, they are to be handled by the invoking code.
MDL-20154 quiz: Remove unused random questions

When a random question is removed from a quiz, and it is not
in use elsewhere, it should be deleted.
MDL-45767: Fixed DB error when returning to course from external tool

The instance ID is not always returned from the external
tool provider.
MDL-45846 Libraries Reinstate custom user agent device detection
MDL-45574 Backup progress: Can time out with large number of files

When there are many files inside a single resource, it's possible
for the backup to time out because it does not report progress
while adding entries to the backup_ids table.
MDL-29708 Fixed extra slashes in $string['storedfilenotcreated'].
MDL-29708 Fixed file_exception() arguments in rename().
MDL-44711 navigation: improved expandable course calculation