Remove portal (fake) app, move tests to courseware.

lms/djangoapps/courseware/features/common.py

lms/djangoapps/courseware/features/courses.py

lms/djangoapps/courseware/features/courseware.feature

lms/djangoapps/courseware/features/homepage.feature

lms/djangoapps/courseware/features/homepage.py

lms/djangoapps/courseware/features/login.feature

lms/djangoapps/courseware/features/login.py

lms/djangoapps/courseware/features/openended.feature

lms/djangoapps/courseware/features/registration.feature

lms/djangoapps/courseware/features/registration.py

lms/djangoapps/courseware/features/signup.feature

lms/djangoapps/courseware/features/signup.py

lms/djangoapps/courseware/features/smart-accordion.feature

lms/djangoapps/portal/README.md

lms/djangoapps/portal/__init__.py

lms/djangoapps/portal/features/factories.py

lms/envs/acceptance.py