Revert "Pwattenberger/sailthru" (#12701)

common/djangoapps/student/cookies.py

common/djangoapps/student/views.py

common/djangoapps/util/model_utils.py

lms/djangoapps/email_marketing/__init__.py

lms/djangoapps/email_marketing/admin.py

lms/djangoapps/email_marketing/migrations/0001_initial.py

lms/djangoapps/email_marketing/migrations/__init__.py

lms/djangoapps/email_marketing/models.py

lms/djangoapps/email_marketing/signals.py

lms/djangoapps/email_marketing/startup.py

lms/djangoapps/email_marketing/tasks.py

lms/djangoapps/email_marketing/tests/test_signals.py

lms/envs/common.py

requirements/edx/base.txt