ECOM-441

Remove course_from_id
don't fetch whole course when the root will do
don't fetch even the root if the id will do
check for definition.data == null

Conditional on existing flag BYPASS_ACTIVATION_EMAIL_FOR_EXTAUTH

Makes small changes in lms and cms both so that user's go to the
original page they intended to if they weren't already logged in

This commit updates common/djangoapps.

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]

add new feature to make sure we aren't writing PII into the application logs. So far we're aware of doing so regarding Auth use-cases

Caution! This is backwards incompatible

LMS-750

before redirecting to SSL authentication.

I also removed conflicting implementation of SSL_AUTH_IMMEDIATE_SIGNUP
and rebased on the current master.

Several pylint fixes and bad super call

This adds a feature flag: AUTH_USE_MIT_CERTIFICATES_IMMEDIATE_SIGNUP
that does an automatic signup of users if they are using external authentcation.

* Fix open redirect vulnerability
* Add Logging To AUDIT_LOG : Note I had to change existing tests
  that mocked AUDIT_LOG with this
* Use external_auth.views.SHIBBOLETH_DOMAIN_PREFIX in student.views
* Add a bunch of documentation
* PEP8 / Pylint

* If a shib users type in their email on the regular login page,
  redirects them to /shib-login/
* Modify student.views.accounts_login to handle redirects
  generated by @login_required for courses that use shib for
  access control.
  Redirect those logins to /shib-login/?next=