Merge pull request #5961 from edx/dan-f/cohort-csv-upload

CHANGELOG.rst

...goapps/student/management/commands/create_random_users.py

common/djangoapps/util/file.py

common/djangoapps/util/tests/test_file.py

common/static/js/spec_helpers/ajax_helpers.js

common/test/acceptance/pages/lms/instructor_dashboard.py

...est/acceptance/tests/discussion/test_cohort_management.py

common/test/acceptance/tests/lms/test_lms_staff_view.py

common/test/data/uploads/cohort_users_both_columns.csv

.../test/data/uploads/cohort_users_missing_cohort_column.csv

...n/test/data/uploads/cohort_users_missing_user_columns.csv

common/test/data/uploads/cohort_users_only_email.csv

common/test/data/uploads/cohort_users_only_username.csv

lms/djangoapps/django_comment_client/base/views.py

lms/djangoapps/instructor/tests/test_api.py

lms/djangoapps/instructor/views/api.py

lms/djangoapps/instructor/views/api_urls.py

lms/djangoapps/instructor/views/instructor_dashboard.py

lms/djangoapps/instructor_task/api.py

lms/djangoapps/instructor_task/models.py