Add scope/field selector settings for LinkedIn provider.

This change adds three new configuration variables to third_party_auth's LinkedIn provider:

* SOCIAL_AUTH_LINKEDIN_OAUTH2_SCOPE,
* SOCIAL_AUTH_LINKEDIN_OAUTH2_FIELD_SELECTORS,
* SOCIAL_AUTH_LINKEDIN_OAUTH2_EXTRA_DATA

Being able to configure these additional settings is useful if you want
the LinkedIn provider to pre-populate the email field when a new user
registers via the linkedin provider.

The Google provider prepoulates the email field by default, but if you
want LinkedIn to do the same, these two settings should be set to:

SOCIAL_AUTH_LINKEDIN_OAUTH2_SCOPE = ['r_basicprofile', 'r_emailaddress']
SOCIAL_AUTH_LINKEDIN_OAUTH2_FIELD_SELECTORS = ['email-address']

For more info see:
http://psa.matiasaguirre.net/docs/backends/linkedin.html
Add redirect.
Add url redirect to.
Update error code.
Fix unit test.
Move js import into courseware js group.
Use confirm dialogue.
Prevents students from accidentally changing their enrollment on login (LMS-2773)

skip tests if not run in lms
Fix unit test.
Initial draft moving key creation out of wiki
Review draft, one more flowchart to come
Additional flowchart
some of Sylvia's edits
Added Brandon DeRosier to authors
Datetime localized on gitlog page of sysadmin dashboard
Completed edits for Sylvia's review. Added data czar to glossary
Change 'Course Name' to 'Course Run' in settings.html

The code behind uses course run to fill this field, so maybe the filed's name should be changed as well?
Adds is_xblock_visible_to_students
Numbering issue
consolidate new post form variants into single client-side template/view