MDL-41087 Backup: add progress tracking in slow steps

Adds calls to the new backup progress tracking API within various steps of the
backup system - previously it only tracked progress between steps, but some steps
can themselves be slow. This ensures the system displays progress (either by
moving the progress bar if possible, or by making the wibbler below it pulsate)
during nearly all of the backup process.
MDL-41733 auth_cas: Allow direct authentication with CAS to a course when multiple authentication is activated
Merge branch 'MDL-41087-master' of git://github.com/sammarshallou/moodle
Merge branch 'MDL-41733_master' of git://github.com/StudiUM/moodle
MDL-40047 events: Add events related to feedback responses

Adding following events related to feedback responses:-
/mod_feedback/event/response_deleted
/mod_feedback/event/response_submitted
/mod_feedback/event/instances_list_viewed
/mod_feedback/event/course_module_viewed
MDL-40047 feedback: Add a test generator for feedback
MDL-40047 events: Add unit tests for feedback events
MDL-40047 events: Replace add_to_logs with new events in feedback