MDL-42598 quiz variant randomisation not random enough.

A student would get the same question variants (for example for a
calculated question) on their first attempt at both copies of a
duplicated quiz.
MDL-33536 navigation: hide hidden categories from the navbar
MDL-42672 blocks: warnings on /mod/xxx/index.php for frontpage course
MDL-42723: Hide and handle LDAP error when user not in context being checked

MDL-41304 only fixed the case when 'Search subcontext' is enabled. We need to
fix the case when it's not enabled too.

While silencing errors with an @ should be avoided if possible, there's no
other way to prevent the warnings in this case.
MDL-42711 ported less style for chat from learnmoodle. added ability to choose course theme's css - this will use ONLY the css available from the theme to style this chat box.
Automatically generated installer lang files
MDL-42711 hide course theme option for non bootstrapbase based themes. some other minor fixes too.
MDL-42711 import learnmoodle fixes: Fix the broken links in RSS feed block

If the <description> of the feed contains URLs longer than 30 characters, the
URL is split because of the break_up_long_words(). When combined with the
filter that converts URLs to links, this produces broken links.

The proper solution would be to improve break_up_long_words() so that it does
not modifies URLs at all. As a temporary solution for our purpose now is to
call format_text() prior to break_up_long_words() as it will not modify the
inner content of the <a> tag.

This should be fixed upstream. See also discussion at
https://moodle.org/mod/forum/discuss.php?d=34947
MDLSITE-2455 Do not throw coding exception when the activity is not found

Under certain conditions, coding exception is thrown when fetching items from
the navigation bar. The patch prevents them. See more details in the tracker.
MDLSITE-2493 glossary filter alert dialog button string now translatable

Conflicts:
	filter/glossary/yui/build/moodle-filter_glossary-autolinker/moodle-filter_glossary-autolinker-debug.js
	filter/glossary/yui/build/moodle-filter_glossary-autolinker/moodle-filter_glossary-autolinker-min.js
	filter/glossary/yui/build/moodle-filter_glossary-autolinker/moodle-filter_glossary-autolinker.js
	filter/glossary/yui/src/autolinker/js/autolinker.js -- M.core.alert api was changed.
MDL-42790 essay attempt on last: fix plain reponse mode

Plain responses, without files, were getting messed up by the
fix for MDL-39980. Something that looked like an HTML comment was being
appended.

This fix works by avoiding appending anything if there are no files. The
new unit test (which was failing before I fixed the code) confirms that
this works. The other tests should be enough to verify that there are no
regressions.
MDL-42808 library: Google API was resetting the timezone
MDL-42711 theme port from LM - this makes the li's link inherit similar size from higher up in cascade.
MDL-42711 theme port from LM: fixed up choice results table overflowing to the right. (MDLSITE-2497)
MDL-42503 treat $CFG->filterall as a real cache flag - verify during cache resets
Automatically generated installer lang files
MDL-42827 JavaScript: Use a more specific selector for activity links
MDL-42711 theme port from LM: MDLSITE-2480 fixed up course view - icon now positioned correctly when long course titles wrap on small screens
MDL-42711 theme port from LM: MDLSITE-2463 wrap tinymce instances responsively on mod/data pages (editing) for smaller screen widths
MDL-42711 added chat.less file