This change includes a build to fix all minified file changes in Moodle
as a result of upgrades to our build process.

* Add a more descriptive label for the next and previous buttons so that
the users would know that clicking on the next or previous buttons will
save the changes they made before proceeding to the next user.
* Add an sr-only div with aria-live to the user picker to let the grader
know the current user that is being graded.
* Hide the user picture from screen readers

Part of MDL-66074

This change modifies the return val for all of the grading functions to
allow them to add additional information.
This means that a grading service can suppress a Grade saved message if
there were no changes, for example.

This also adds a distinction between:
- Errored (Exception thrown in the WS call)
- Failed (Warning in the output of the WS call)
- Success (Grade actually saved)
- None of the above (No save, no fail, no change)

Part of MDL-66074

Part of MDL-66074

Part of MDL-66074

Part of MDL-66074