Implement a skeleton page with Bootstrap

LEARNER-1174

Do not capitalize words in start button

Learner-1146

Fetched Programs and Program details from Course Discovery service for all sites and stored the uuids in cache with site-specfic keys.
Learner-1146

Replace urls in html updates.

Bump up the NewRelic plugin version

Most bugfixes are python3 or Tornado specific, but several releate
to Django 1.10 and they improved transaction traces since we last
updated.

https://docs.newrelic.com/docs/release-notes/agent-release-notes/python-release-notes/python-agent-286370

[ENT-457] Fix failing course_mode tests

fix issue where video modal is not closed by clicking outside the video

Rename xss linter.

Change to validate=False which emulates django-storages

[ENT-457] Create EnterpriseCourseEnrollment when enrolling via Track Selection page

This requires the next commit to work, but needed to be
is a separate commit to keep history.

eslint config edx v3

On many buckets, we use s3://bucket/path to separate environments
because AWS used to have a really low limit on the number of buckets
we could have, and we wanted to share them across environments.

If you combine this with an IAM policy that only allows you access
to the s3://bucket/path that you "own", then get_bucket fails.
http://boto.cloudhackers.com/en/stable/ref/s3.html#boto.s3.connection.S3Connection.get_bucket
The HEAD appears to be similar to get_all_keys which requires
ListObjects on the bucket with no conditions.

django-storages (Which is what we write new S3 access in) actually
always passes validate=False unless you're allowing it to create buckets
for you (which we never do).
https://github.com/jschneier/django-storages/blob/1.4.1/storages/backends/s3boto.py#L320-L334

EDUCATOR-793: converts TypeError,NotFoundError logging to debug only

LEARNER-1604: Change default and refactor old unified_course_view flag.

Enqueue Generate Certs Task on Passing Grade

Merge pull request #15223 from proversity-org/proversity/pr-add-invitation-only-field-to-course-serializer

Add invitation_only field to course serializer

Remove deprecated django.utils.importlib

Correct spelling of 'Open edX', and pedantic typography in the copyright footer

fixing color contrast issues in studio

PLAT-1597 Fix test mongo cleanup hostname in Docker devstack

This includes several general enhancement in addition
to the fixes for unified_course_view:
1. Add support for default when no waffle flag defined.
2. Add support for table_blacklist to assertNumQueries.
3. Rename flag to 'course_experience.course_outline_page'.
4. Change flag default to True when it is not defined.

PLAT-1610 Fix social auth config error in Docker bok-choy tests

PLAT-1323 Remove older, slower code path for course export