MDL-34989 assign: Allow students to submit when grade is overriden

Also inform teachers when grading is disabled due to gradebook lock/override.
MDL-34989 assign: Do not add a param to grading_disabled - cannot be backported.
MDL-40126 Enrolments: Implemented two webservices to get enrolment instance info

1. core_enrol_get_course_enrolment_methods() which returns all enrolment method instances
which implement get_enrol_info()
2. enrol_self_get_instance_info() will return information about self enrolment instance.
MDL-41024 lib: deprecate isediting
MDL-41025 moodlelib: addressed todo on truncate_userinfo
MDL-41034 fix TinyMCE managefiles plugin for textareas that do not support file uploads

The current managefiles plugin assumes that every file manager will be created
by either calling use_editor without filepicker options ($fpoptions) or with
filepicker options that include options for the moodleimage plugin.
Merge branch 'MDL-34989-master' of git://github.com/damyon/moodle
MDL-40086 file: Correct ordering of subdirectories

Thanks to Mohamed Alsharaf for the proposed solution.
Merge branch 'MDL-41034-essay-broken' of git://github.com/ktemkin/moodle
MDL-41034 Additional check to be extra sure that no JS error occurs
Merge branch 'MDL-40682-master' of git://github.com/ankitagarwal/moodle
MDL-40682 MDL-41000 event name and description return strings

event description is non-localised string
Merge branch 'MDL-40935-master' of git://github.com/ankitagarwal/moodle
Merge branch 'wip-mdl-40126' of git://github.com/rajeshtaneja/moodle
Merge branch 'wip-MDL-41024-m26' of git://github.com/samhemelryk/moodle
Merge branch 'wip-MDL-41025-m26' of git://github.com/samhemelryk/moodle
MDL-40438 migrate all collatorlib:: and textlib:: uses
MDL-41023 weblib: improved coding style
Merge branch 'w32_MDL-40438_m26_textlib' of https://github.com/skodak/moodle

Conflicts:
	lib/weblib.php
Merge branch 'MDL-40086-master' of git://github.com/FMCorz/moodle

Conflicts:
	lib/filestorage/file_storage.php