* Change settings default
* Set `ENABLE_CREATOR_GROUP` to False for devstack
* Set `ENABLE_CREATOR_GROUP` to False for tests

In f095c5fe it was decided to enable
anyone to make courses in Studio by default in order to make things
easier in dev environments. This was before the code was open source.
This default is likely in effect for many Open edX instances, but almost
no one would want this setting outside of development.

Cherry picked from #15343 6b085281.

(cherry picked from commit c567add6)

(cherry picked from commit fdd974dd)
(cherry picked from commit 292502ba)

LEARNER-1798

PLAT-1499 Use appropriate default settings in Docker devstack

Reduce xss thresholds.

Add flag to configure whether "Notify users by email" is checked by default.

Keep button shape for long strings

Removed old (unused) devplus.py env for LMS.

Override video xmodule's youtube id with the id coming from val YT profile

Implement a skeleton page with Bootstrap

LEARNER-1174

This used to be where we enabled some prod-like features on the dev
environment, but it's horribly out of date (it actually predates
the vagrant-based devstack).

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