MDL-40368 tool_capability: overall improvements made

* Can now compare multiple capabilities at the same time.
* Capability search now persists between requests.
* Upgraded to use renderers.
* Upgraded module.js to YUI shifted module.
* Converted deprecated calls.
* Converted forms to Moodleforms.
* Implemented backend functionality to overview at
  different context levels. Not possible presently as
  there are no front end hooks.
MDL-40386: Fix for updating timemodified field in book_chapters
MDL-40368 tool_capability: clean up as per notes from peer-review.

* Coding style clean up.
* SQL indentation
* Removal of non-matching capabilities when searching.
* Fixed notices/warnings when hitting enter on search.
MDL-40434 calculatedmulti multiple-response questions not randomised
MDL-38314 repository: Remove orphan repository instances
MDL-38314 repository: Delete repository instances on context deletion
MDL-38314 repository: Unit Tests for delete_all_for_context()
MDL-38314 repository: Improving performance of upgrade script
MDL-40401 Libraries: load_temp_role() and remove_temp_roles() can not be used any more.
MDL-40402 libraries: Replace get_system_context() with context_system::instance() in core
MDL-40402 unittests: Make sure get_system_context() throws a deprecated warning
MDL-40402 libraries: Deprecate get_system_context()
MDL-40402 libraries: update the mistake in comment
MDL-40318 quiz intro comprising just an impage was not shown

Also, ensure that we don't output an empty box if there are no access
messages.
MDL-40499 Edit question from 1.9 backup breaks if images in subdirs
MDL-40500 move MOODLE_INTERNAL define before core_component include

This resolves problems with MOODLE_INTERNAL in db/subplugins.php
MDL-40415 add explicit OPcache support
MDL-37484 SCORM: disable toc in player when using direct AICC url
MDL-40243 use suspended flag in auth_enrol instead of nologin auth
Merge branch 'w28_MDL-40415_m26_opcache' of https://github.com/skodak/moodle