MDL-41071 core: plugininfo_mod caches in plugininfo_mod definition
MDL-40952 skip only the opcache requirement in environment test

Please note we need other optional extensions and settings because otherwise some tests fail without explanation.
MDL-41094 purge caches only before and after upgrade of plugins

It should not be necessary to purge before/after individual plugins
because caches are disabled during install and upgrade.
MDL-41112 fix theme and js caching info in config-dist.php
MDL-41125 course: Only require dndupload library when necessary
MDL-41122: Trim on RSS body to prevent Remote RSS block from failing on valid feeds
MDL-41136 badges: Prevent extra loading due to unnecessary includes
MDL-39474 introduce $CFG->debugdeveloper and cleanup $CFG init
MDL-41159 theme: Remove z-index from file manager context menu icon
MDL-29004 Wiki: display images in printer-friendly view
MDL-39956 cohort: Convert to new events

* \core\event\cohort_created
* \core\event\cohort_updated
* \core\event\cohort_deleted
* \core\event\cohort_member_added
* \core\event\cohort_member_removed
MDL-39956 cohort: Add tests for new events
MDL-39956 cohort: Event clean up and made ready for integration

* Added more PHP Documentation
* Localised strings for get_name()
* get_legacy_eventname() is now static
* get_legacy_eventdata() is now protected
* Testing legacy event data
* Added missing defined('MOODLE_INTERNAL') checks
* Added missing call to add_record_snapshot()
MDL-41157 calendar: add unit tests for calendar_get_course_cached
MDL-41157 calendar: improve calendar_get_course_cached

The function get_course() introduced in 2.5.1 will use $COURSE and
$SITE to avoid an uncessary DB query, simplifying the logic of this
function and improving perf.
MDL-40709 skydrive: filter files by accepted types

This means images will only be shown in the image picker, videos
in the video picker - etc.
MDL-41209 tool_uploadcourse: Remove faulty form validation
MDL-41211 tool_uploadcourse: Passing restore file path to processor
MDL-41191 forum: unit tests for forum_get_courses_user_posted_in
MDL-41191 forum: convert use of deprecated function