MDL-41593 admin: use default setting if preventexecpath active

This resolves problems when installing Moodle
and addons when preventexecpath active.

Please note the admin_setting_configfile is still
incorrectly restricted - this will be resolved by
MDL-40949.
MDL-47555 core_availability: Issue with page layout & grade restriction

* Set pagelayout before getting section info, otherwise conditional activity renderers will default to the default 'base' layout.
MDL-47499 tasks: Scheduled tasks custom schedule is reset on upgrade.

Add a unit test for reset_scheduled_tasks_for_component and make sure it doesn't clear
customised schedules for existing tasks.
MDL-47632 calendar: Fixed iCal link going blue after visiting it
MDL-47704 Grades: Fix for set_usedinaggregation

Used in aggregation was not resetting previously set values
when recalculating an aggregation. This meant that items no longer
in the aggregation, were displayed with stale weights in the user report.
MDL-38065 gradebook: Fix issue with hidden categories breaking rowspan.

Hidden subcategories break the rowspan in the gradebook; this fix corrects
the calculation of the rowspan.
MDL-46133 tool_monitor: added event cleanup task
MDL-46133 tool_monitor: added unit tests
MDL-47664 phpunit: Do not use sequence number changes for Oracle

When resetting a sequence number, we call change_database_structure()
which in turns clears the MUC cache for databasemeta. This cache contains
information about the table, columns, etc.

After the cache is cleared, it must be re-filled, and it was discovered
that the get_columns() code which fills this cache can take a particularly
long time. Given that this is called for every table in Moodle, this can
add up to a significant period, and this is done on a per-testsuite basis.

On my SSD install this was taking approximately 40 seconds on each re-fill
of the cache.
MDL-47738 gradereport_history: User selector handles broke with 0 user

It was impossible to reopen the dialogue when the last search result
did not return any user.
MDL-47737 editor_atto: Prevent false negative when saving draft on IE9
MDL-38172 Lesson: Additional Info not displayed at end of lesson
MDL-47735 core: prevented iteration of 'groupmembersonly'

The course module variable 'groupmembersonly' was removed in 2.8.
MDL-47728 tool_monitor: added capability check before displaying link
MDL-47684 mod: better validation of rating options
MDL-47752 grading: fixed bugs with the modgrade element
MDL-46499 navigation: better enrolled course limit

We now user $CFG->navcourselimit to limit the number of
courses shown in the navigation when browsing another users
full profile. Previously it showed all courses which caused
some slowdown.
MDL-47077 report_participation: fixed pagination in groups
MDL-47754 install: fix redirect loop
MDL-47735 mod_forum: added 'My profile' -> 'Forum posts' behat test