* 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.
Switching between categories view and edit no longer depend on global editing mode
/course/index.php and /course/category.php do not contain editing code
* Note: this would never lead to problems with default role definions.
* Also ended up mostly rewriting delete_category_form to simplify the messages that are displayed.
* New helper function require_all_capabilities, a bit like require_any_capability.
Bugs: MDL-17479, MDL-16426, MDL-16063, MDL-16013, MDL-15658, MDL-15556, MDL-15161, MDL-14925, MDL-13742, MDL-11557.
* Simplify category editing permissions to just moodle/category:manage and moodle/category:seehiddencategories.
* Enforce those correctly. (Note MDL 17502 is still outstanding.)
* Don't screw up category sort order when you just edit name or description.
* Niceties like where redirects go when you cancel or submit forms.
* Make sure a global course creator can see the site admin block.
* Don't allow a category to be made the child of one of its children!
* General code cleanup to bring key files more in line with best pracitice.
Apologies for the fact it is one big patch, rather than a series of smaller patches. However, categoryedit.php, category.php and index.php where in pretty bad shape and needed significant cleaning up. categoryedit.php, in particular, was almost completely rewritten.
Merged from MOODLE_19_STABLE.
