CSV Reporting of Shopping Cart Purchases, with tests

lms/djangoapps/shoppingcart/admin.py

...urseregistrationannotation__add_field_orderitem_report.py

lms/djangoapps/shoppingcart/models.py

lms/djangoapps/shoppingcart/tests/test_models.py

lms/djangoapps/shoppingcart/tests/test_views.py

lms/djangoapps/shoppingcart/urls.py

lms/djangoapps/shoppingcart/views.py

lms/envs/aws.py

lms/envs/common.py

lms/static/sass/views/_shoppingcart.scss

lms/templates/shoppingcart/download_report.html

requirements/edx/base.txt