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.
Explicitly skip tests in common unless we know we're running the LMS unittest suite
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
Add test that xml body was parsed successfully.
Review draft, one more flowchart to come
Additional flowchart
some of Sylvia's edits
Display names, help text, and "deprecated" for Advanced Settings.

STUD-302, STUD-303
Merge pull request #4073 from edx/christina/advanced-settings-hack

Display names, help text, and "deprecated" for Advanced Settings.
Enable Mixed Modulestore STUD-1540
Refactor get_parent_locations STUD-1663
Merge pull request #3915 from edx/studio/uses-mixed-modulestore

Enable mixed modulestore
Fix saving error of video editor in non-english translation

Currently the code in ```tabs-aggregator.coffee``` uses the display name of a tab as the key to index the current tab. When a non-english translation is applied, the javascript code will get localized names instead of the original english names, which causes the following ```getValue``` function fails as it cannot reference the correct tab.
Use the 'data' attribute to store the original tab name.