remove explicit middleware from resolver task

Address Gabe's comment

Add TODO to define middleware_classes in settings

Before this commit, XBlock static assets were extracted during the
collectstatic process by iterating through all installed XBlock classes
and creating a separate directory for each. However, some packages
install many XBlocks that actually share the same static assets. The
most notable example is problem_builder, though we also see this with
schoolyourself and google_drive.

This commit uses the parent module name to do package asset lookup,
collapsing those cases down and eliminating duplicates. For a default
install of edx-platform XBlocks, this reduces assets generated from 31M
to 14M.

This method will retrieve the Course Run information from the Discovery
service based on a Courses UUID.

[LEARNER-3160]

Move mimetype addition to common initialization.

Anonymous users may now view units in the courseware. This access is limited to units that are not considered problems/graded (e.g. homework, exams).

- Remove usage of django.urls.patterns
- Change urls tuples to lists
- Make all string view names callables

- Enables a method of deriving Django settings from other Django
  settings after all other Django settings are stable.

django.util.unittest was deprecated in django 1.7 and removed in 1.9.

PLAT-1551

LEARNER-2307

In particular, implement a validation API for registration,
where a client makes AJAX calls to the endpoints requesting
validation decisions on each input. Responses are strings
dependent on the type of validation error; if no error,
then empty string to indicate OK.

with a custom patch needed by edx-platform.
Upgrade django-filter as well to v1.0.4
Import DjangoFilterBackend from the correct module - django_filter.
Add django-filter to INSTALLED_APPS.

It accounts for a large chunk of our splunk logs and is often
repetitive.  See forums connections which on a sandbox do:

```
Starting new HTTP connection (1): localhost
```
and
```
comment_client_request_log: request_id=06ac65d3-61b9-4882-9edb-c6b65709318a, method=get, url=http://localhost:18080/api/v1/users/5, duration=0.0101051330566
```

Add this for any other IDA call.

EDUCATOR-565 | Add POLICY_CHANGE_GRADES_ROUTING_KEY, fix errors in compute_all_grades_for_course circuitry.

In production environments, the DiscussionXBlock was generating CSS and
JS asset URLs that pointed to the unminified versions of those bundled
assets. Due to our nginx rules, this would cause the assets to be
served without the long expiration times, forcing the user's browser to
constantly refetch these assets while browsing a course.

[PERF-431]

Learner-1111

The internal_api_url field has been deprecated. All usages have been updated with calls to the method get_internal_api_url().

LEARNER-1111

This reverts commit f97f0525, reversing
changes made to 800bcd8e.

Also add it to the course home page.

Although we are phasing out our support of OIDC, this particular feature will allow us to eliminate many of the settings we
share across services. Instead of reading various endpoints and secret keys from settings or hardcoded values, services
with the proper authentication backend can simply read (and cache) the information from this endpoint.

ECOM-3629