MDL-48144 upgrade: add v2.8.0 sep lines
MDL-48168 quiz editing: max grade should be editable after attempts

Note that there was a lot of legacy code left from Moodle 2.7 which is
no longer required, and I took this opportunity to delete it.
MDL-43628 assign: make submissionagreement usable on multilingual sites
MDL-47648 admin unit tests: fix file perms on mimetex.exe

This was causing the
core_admintree_testcase::test_admin_setting_configexecutable unit test
to fail.
MDL-48156 task: Skip the scheduled task only for really disabled plugins
MDL-39376 enrol: Optimized setting for ldap and database
MDL-46116 mod_imscp: Don't create links on items without content.
MDL-47618 quiz statistics: fatal error with groups.

The problem was that the names of query placeholders were changing. The
fix was to do things ourself, rather than using get_in_or_equal.
MDL-46116 mod_imscp: Display first item with content on load.
Merge branch 'MDL-48168_28' of git://github.com/timhunt/moodle into MOODLE_28_STABLE
MDL-48093 HTML 5 video: Firefox now supports .mp4
MDL-47975 assign: Stop gap fix for random time fails.
MDL-47502 test_statslib_cron_daily: fix provider

Fiddling with the database in the data provider causes "out of sync"
errors when running suite tests.
MDL-47502 statslib tests: improve test

While integrating I noticed some problems which already existed in this
test:
* The enrolment data generator was not used
* The student roleid was hardocded
* The role assignment was at site level..
MDL-30968 mod/forum Fixed group link
MDL-48115 badges: Fix strtoupper() output in badges

Signed-off-by: Yuliya Bozhko <yuliya.bozhko@totaralms.com>
MDL-39692 grade: Ability to delete letter boundary
MDL-39692 grade: Little code clean up of letter boundary deletion
MDL-47391 Update pagelayout for default profile configuration
MDL-46416 group: Use a revision number for group pictures