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-38172 Lesson: Additional Info not displayed at end of lesson
MDL-47754 install: fix redirect loop
MDL-47739 form: Calendar widget causes unintentional focus and scroll
MDL-47489 core_grades: Adjust weights of extra credit items for Natural
MDL-47503 Grades: Completely remove aggregationsubcats

This setting is not compatible with combinations of aggregation methods
and the ways in which it does and does not work are not documented. It
was voted to remove it completely by the gradebook workshop, so I have
completely removed it and added a warning for all affected courses + restored
backups.
MDL-47736 editor_atto: only save/restore draft when necessary
MDL-47489 core_grades: Adjust weights of extra credit items for Mean
MDL-47489 core_grades: Adjust weights of extra credit items for Simple
MDL-47489 core_grades: Behat tests covering contributions with extra credit
Merge branch 'MDL-38065-fix-master' of git://github.com/jmarthaler/moodle
MDL-47725 gradereport_user: Only hide grades when they were altered

The method blank_hidden_total_and_adjust_bounds() now checks for more
than just a grade change, and in that cause would hide the grade. We
added a condition to only hide the grade when it effectively changed,
not when its other properties have.
Merge branch 'MDL-47725-master' of git://github.com/FMCorz/moodle
Merge branch 'MDL-47736_master' of git://github.com/markn86/moodle
Merge branch 'MDL-47489-master' of git://github.com/FMCorz/moodle
MDL-47400 gradereport_history: Ensure float precision is enforced

Format floats according to the grade item config.
MDL-47503 Grades: Display the notice about upgraded grades on all grade report pages.

Moved this to the print_grade_page_head function and added an access check so it only
displays for teachers.