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

Also inform teachers when grading is disabled due to gradebook lock/override.

Conflicts:

	mod/assign/locallib.php
MDL-34989 assign: Do not add a param to grading_disabled - cannot be backported.

Conflicts:

	mod/assign/locallib.php
MDL-27953 auth: allowed the LDAP plugin to be manually assigned to uploaded users
MDL-40662 block_course_overview: added addinstance capability to remove debugging message due to system context being used on the 'Default My home page'
MDL-35927 filepicker: add aria attribute to display modal error
Automatically generated installer lang files
MDL-36011 tablelib: Make column headers expand/collapse links accessible.

Conflicts:

	theme/base/style/core.css
	theme/bootstrapbase/less/moodle/core.less
	theme/bootstrapbase/style/moodle.css
MDL-40889 prevent 304 when minimising JS
MDL-31226: quiz: Fix message for attempts built on previous.

At the moment, when attempt is built on the last one, "not yet answered"
message is shown, which confuses many people. This patch modifies the state to
"complete" for attempt based on previous and modifies the output string.

Many thanks to Tim Hunt for guiding me through quiz infrastructure and some code
suggestions.
MDL-34785 performance improvement with big list of courses
MDL-35981 comments: Make delete comment keyboard accessible.
MDL-35981 comments: Add comment about keycodes for space and enter.
MDL-35981 comments: Fix for keyboard control of "add a comment"
Merge branch 'MDL-35981-24' of git://github.com/damyon/moodle into MOODLE_24_STABLE
Merge branch 'MDL-35927_m24' of git://github.com/rwijaya/moodle into MOODLE_24_STABLE
Merge branch 'MDL-34989-24' of git://github.com/damyon/moodle into MDL-34989-24
MDL-30852 grade report: Add aria attributes

Converted to git branch by Damyon
MDL-30852 grade: Coding style fix for user report.
MDL-30852 grade report: More coding guideline cleanups.
Merge branch 'MDL-35922-24' of git://github.com/phalacee/moodle into MOODLE_24_STABLE