MDL-45538 files: restore missing records in draft areas
MDL-47966 Add default content type and encoding
MDL-47903 mod_forum: Add discussion subscription time

This helps us to only send notifications for messages the user should have
already seen.
MDL-47903 mod_forum: Correct test fails related to caching and time

This adds a reset of the discussion and forum cache when running the mail
and maildigest tests.

These test fails were highlighted by the addition of new tests which
add similar post ids.
MDL-47207 mod_forum: Unifying criteria
MDL-26447 gradebook: Default gradedisplaytype fixed for all locales
MDL-47987 mod_forum: Users subscribe to discussions not forums

Correct language string which describes users subscribing to a discussion,
and use it when subscribing on post.
MDL-47864 grade_report: Edulevels according to default user permissions
MDL-47864 tool_monitor: Change edulevels

Considering that the most common use case
to manage rules is an admin CRUDing them.
MDL-47976 tool_monitor: fix ordering in unittest
MDL-45204 phpunit: Fixed test_localcachedir test

make_localcache_directory is the first call to make
localcache, which is already created by reset. So deleting
existing localcache directory will pass this test
MDL-47758 tool_monitor: prevent DB error when revisiting a delete URL
MDL-47758 tool_monitor: altered behat tests so they pass
MDL-48008 gradeimport_xml: report errors usefully
MDL-48010 grade import from URL: don't corrupt the URL.
MDL-47968 mod_forum: fixed search form HTML5 validation
MDL-47969 mod_survey: fixed HTML5 validation of index.php
MDL-47917 cachestore_memcached: fixed get_many ordering
MDL-47361 tooL_monitor: string and UI changes
Merge branch 'wip_MDL-47966_m28_defaultheaders' of https://github.com/skodak/moodle