Also rename course_in_list -> core_course_list_element
Deprecate class coursecat_sortable_records

Replace calls to \coursecat::get_all() or cache the results.

A user should be able to remove an idnumber from a category, also 0
should not be allowed multiple times.

Remove sleep() and replace with waiting for a second to roll over,
this results in a simpler call the guarantee time() has moved forward

Cover new option "requiredcapabilities".

Newly introduced unit tests are failing because the timestamps used are
too large.  Example timestamps were 11 characters long instead of 10.

MDL-45847 resort: Add more course sorting options

Add descending sort options and course timecreated sort options.
Includes behat and unit test changes.

* Implemented a new course and category management page.
* Deprecated the old management interface.
* Unit tests to cover the new API and core functions.
* Behat tests to cover the new interface.

Also search_courses_count(), get_courses_count();
Added unittests

- Course categories caches are purged by event now
- session cache has additional 10 minutes ttl to clear itself and accomodate for permission changes that do not trigger event purging
- additional request-level cache for coursecat::get()
- We store only children of one category in one cache key
- Function coursecat::get_children() can return results sorted and/or paginated. Added tests

- Retrieve and cache only often-used fields of course category
- Removed function coursecat::get_all_visible() as potentially causing performance issues
- removed function coursecat::get_all_parents() as ineffective and unnecessary, replaced with get_parents()
- retrieve all fields from course_categories when unretrieved field is accessed

Also some code improvements:
- rename functions starting with _ , rename arguments, etc.

MDL-38147 Added coursecatlib_test.php, changed other tests to use coursecat::create() for creating category