Use http or https, depending on the value of `request.is_secure()`.
That is how links in most other emails are handled.

Fix acceptance and unit tests

LMS-1296

This commit adds the non-courseware lms/djangoapps and lms/lib.

These keys are now objects with a limited interface, and the particular
internal representation is managed by the data storage layer (the
modulestore).

For the LMS, there should be no outward-facing changes to the system.
The keys are, for now, a change to internal representation only. For
Studio, the new serialized form of the keys is used in urls, to allow
for further migration in the future.

Co-Author: Andy Armstrong <andya@edx.org>
Co-Author: Christina Roberts <christina@edx.org>
Co-Author: David Baumgold <db@edx.org>
Co-Author: Diana Huang <dkh@edx.org>
Co-Author: Don Mitchell <dmitchell@edx.org>
Co-Author: Julia Hansbrough <julia@edx.org>
Co-Author: Nimisha Asthagiri <nasthagiri@edx.org>
Co-Author: Sarina Canelake <sarina@edx.org>

[LMS-2370]

into beta dashboard.

Also includes new functionality, in both legacy and beta
dashboard, to include appropriate email text for a
Shibboleth course.

This centralizes the logic for group membership, and means that we
don't need to make queries to find out whether the legacy groups names exist.

    Added some text to guide the student to register with a particular email address.
    This is the one that was entered into the enrollment/invitation form by the instructor.
    Modified the template and associated test.

Modified navigation tests to use MixedModulestore
Updated factories to find editable modulestore

Updated test_submitting_problems

Updated test_tabs.py

Updated test_view_authentication

Updated test_views

Updated courseware/tests/tests.py

Updated test_masquerade

Updated test_module_render

Pylint fixes

Updated video and word cloud tests

Updated course wiki tests

Updated license and open_ended tests.
One open_ended test still failing due to Mako initialization issues

Updated staticbook

Updated django_comment_client tests

Updated instructor tests

Updated instructor task tests

Updated external_auth tests

Updated course_groups

Features coming down the pipe will want to be able to:
* Refer to enrollments before they are actually activated (approval step).
* See what courses a user used to be enrolled in for when they re-enroll in
  the same course, or a different run of that course.
* Have different "modes" of enrolling in a course, representing things like
  honor certificate enrollment, auditing (no certs), etc.

This change adds an is_active flag and mode (with default being "honor").
The commit is only as large as it is because many parts of the codebase were
manipulating enrollments by adding and removing CourseEnrollment objects
directly. It was necessary to create classmethods on CourseEnrollment to
encapsulate this functionality and then port everything over to using them.

The migration to add columns has been tested on a prod replica, and seems to be
fine for running on a live system with single digit millions of rows of
enrollments.

Moved xml_store_config, mongo_store_config, and draft_mongo_store_config to xmodule/modulestore/tests/django_util.py
Removed some repeated instances of xml_store_config.
Reverted some changes to mongo_store_config so each modulestore gets it's own uuid.

Optionally email students on enroll/un-enroll actions
by instructor from enrollment tab in LMS.

Note, the students_lc list is used in _do_enroll_students when overload
= True so it needs to be left in.

- Remove single enrollment/unenrollment
- Make unenrollment work with multi-email listbox.
- Provide checkbox for auto-enroll on activate if user not yet signed
up.
- Enroll student when activating if auto-enroll flag set.