Rather than Mako block hack

Rather than Mako block hack

ECOM-2972

Please note that this is a squshed commit and the work of:
Symbolist, macdiesel, nedbat, doctoryes, muzaffaryousaf and muhammad-ammar

Make escaping for json simpler and more consistent in Mako templates
- add escape_json_dumps to escape and json.dumps
- add escape_js_str to escape javascript string
- refactor Studio to use escape_json_dumps in Mako templates

TNL-2646: Escape json.dumps

ECOM-2044

PR #8930

ECOM-1017

TNL-2945

Adding the pyuca to support sorting in differnet languages.

TNL-2047

Fixing the pencil icon issue.

TNL-2047

TNL-1862

TNL-1535

TNL-1499

Add querystring param "course_mode" to the login/registration
page so the user can skip track selection.

This supports upcoming changes to the course details page
that allow the user to choose the track when clicking
"enroll", which will replace the functionality of the track
selection page.

TNL-1493

See https://openedx.atlassian.net/wiki/display/TNL/User+API for details

The new "country access" implementation replaces the old
implementation.  Middleware and tests have been updated
accordingly, but deprecated models are preserved
for backwards compatibility.

Users who are blocked from enrolling in a course
due to an embargo are redirected to the blocked
message page after authentication completes.

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]

Makes logistration available at /login and /register as well as /accounts/login/ and /accounts/register/. In addition:

- Adds support for redirect URLs in third party auth for combined login/registration page
- Adds support for external auth on the combined login/registration page
- Removes old login and registration acceptance tests
- Adds deprecation warnings to old login and register views
- Moves third party auth util to student_account
- Adds exception for microsites (theming)

Internationalize error messages for password reset on the new login page.