MDL-44321 events: cleaning up course_module_viewed event
MDL-44321 events: cleaning up course_module_instance_list_viewed event
MDL-44321 events: debug on errors in add_record_snapshot()

also clone object returned by get_record_snapshot() to prevent accidental changing of $COURSE or other important objects
MDL-44321 events: make sure the full object is passed to add_record_snapshot()
MDL-44321 events: Text correction in assessable events