TNL-3137

This is a squash of 38 commits ending with
5b080f979d692804452400ac5bed9b17c50b001e

* Add action text to social media links.
* Make the alt text for mobile links more descriptive.

Serve branded footer JSON/HTML/CSS/JS from an API endpoint
in the branding app.  Refactor OpenEdX and EdX.org footer templates
to use the Python version of the API, ensuring that the API
values are consistent with the footer included in main.html.

Detailed changes:

* Added footer API end-point to the branding app.
* Footer API allows the language to be set with querystring parameters.
* Footer API allows showing/hiding of the OpenEdX logo using querystring parameters.
* Deprecate ENABLE_FOOTER_V3 in favor of the branding API configuration flag.
* Move no referrer script into main.html from the edx footer template.
* Rename rwd_header_footer.js to rwd_header.js
* Cache API responses.

Authors:
Awais Qureshi, Aamir Khan, Will Daly

(SOL-531)(SOL-532)Course Cards update; A link to course discovery page has been added to the OpenEdX homepage

do the ORG filtering as part of the mongo query. Also, don't trigger metadata inheritence calculations when just trying to load 'about' information, which is not tied into the course tree anyhow (i.e. no parent/child relationship)

Update edx-lint to the version that checks if tearDown uses super.

Convert a number of tearDown methods into addCleanup.

Remove some unneeded tearDown methods: no need to call patch.stopall if
none of them were started with patch.start.

The existing pattern of using `override_settings(MODULESTORE=...)` prevented
us from having more than one layer of subclassing in modulestore tests.

In a structure like:

    @override_settings(MODULESTORE=store_a)
    class BaseTestCase(ModuleStoreTestCase):
        def setUp(self):
            # use store

    @override_settings(MODULESTORE=store_b)
    class ChildTestCase(BaseTestCase):
        def setUp(self):
            # use store

In this case, the store actions performed in `BaseTestCase` on behalf of
`ChildTestCase` would still use `store_a`, even though the `ChildTestCase`
had specified to use `store_b`. This is because the `override_settings`
decorator would be the innermost wrapper around the `BaseTestCase.setUp` method,
no matter what `ChildTestCase` does.

To remedy this, we move the call to `override_settings` into the
`ModuleStoreTestCase.setUp` method, and use a cleanup to remove the override.
Subclasses can just defined the `MODULESTORE` class attribute to specify which
modulestore to use _for the entire `setUp` chain_.

[PLAT-419]

OPEN-307

OPEN-307

OPEN-307

Move modulestore config for tests to an importable location
Disable pylnt warning for lms imports in common tests
Refactor all testcases that loaded all xml courses
TE-610
TE-489

Feature flagged. Puts a checkbox in the iframe. The iframe uses an organization_full_name parameter forwarded from Drupal by the courseware views and POSTs an email_opt_in parameter to the student views, preserving it on 403.

only redirect to dashboard if user has course enrollments, otherwise remain on the course catalog page (aka homepage or root)

update lettuce test to match new expected behavior

add Jason's feedback

only apply new redirect logic for microsites

switch to use a feature flag to determine whether to support redirect behavior

Putting the new edx header behind a feature flag.

LMS-6622

Conflicts:
	cms/djangoapps/contentstore/views/tests/test_container_page.py
	common/djangoapps/external_auth/tests/test_shib.py
	common/djangoapps/student/tests/test_login.py
	common/lib/xmodule/xmodule/modulestore/tests/django_utils.py
	common/lib/xmodule/xmodule/modulestore/tests/factories.py
	common/lib/xmodule/xmodule/modulestore/xml_importer.py
	lms/djangoapps/branding/tests.py
	lms/djangoapps/courseware/tests/test_submitting_problems.py
	lms/djangoapps/courseware/tests/test_video_handlers.py
	lms/djangoapps/instructor_task/tests/test_base.py
	lms/djangoapps/instructor_task/tests/test_integration.py

Refactor get_parent_locations STUD-1663

LMS-2719