MDL-40343 forum: indent less when mobile, nested

Changes the indenting of forum replies to be relative to the width of
the parent container, so the indent decreases as threads get nested
deeper. Also reduces the indent size automatically for smaller screen
sizes.
MDL-46219 assignment: delete files when resetting assign activities
MDL-47569 backup: Escape section summary for XML

This was causing the parsing of the XML
to fail because things like & were not
escaped.
MDL-47569 backup: Do not close questions tag if never opened

This can happen when restoring quizzes that
do not have any questions.
MDL-33939 gradingform_guide: use correct max grade for scales.
MDL-36987 auth_manual: fix config for field locking

Thanks to Sergey for the patch
MDL-29873 Lesson: Essays not shown on grade page with SQL server
MDL-47755 badges: Fix internal message output

Signed-off-by: Yuliya Bozhko <yuliya.bozhko@totaralms.com>
MDL-47805 tool_monitor: More info in adhoc task
MDL-47703 core_grades: Prevent use of weights with non-aggregated scales
MDL-47703 core_grades: Behat test for (non) aggregated scales
MDL-47647 lib: Fix message unit test failure.

Messaging unit tests on Windows were failing because
of a comparison between two file paths. Part of the
path would have a forward slash instead of a backslash
and so would fail.
MDL-47898 mod_quiz: Correct path when checking content_editable

Addresses a number of issues when using the text editor in a quiz using
secure mode.
MDL-47559 user_menu: customusermenu setting
Automatically generated installer lang files
MDL-814 forum: provide cancel button when posting

This is the way to clear atto drafts
MDL-47916 web services: Fixed invalid returned value type
MDL-47914 report_stats: better handling of user and mode
Merge branch 'MDL-47559-master' of git://github.com/jethac/moodle
MDL-47183 post-integration fixes

* Fixed typo with context_module::instance
* Fixed use of $mod->get_context()