Syncs preface with edx-doc repo version

Avoid MultipleObjectsReturned errors with LoginFailures

Added extra field to CCX model for Course Models

Upgrade edx-lint to 0.4.2

Replayed by @efischer19 due to git issues, initially commited by @laq

The get_or_create function is vulnerable to race conditions in MySQL, which can
cause the model LoginFailure to, in some cases, have more than one row for the
same user, breaking the login for that user.

Addinf functionality to expect and clean the error by deleting extra rows (by
oldest lockout date), leaving just one entry and allowing the user to login.

Replayed and squashed by @efischer19, initially commited by @laq

MA-1919 making mobile handout links accommodate jump to id's and cour…

Incremented edx-proctoring version to 0.12.11

Fix subsection config for self-paced course

REST APIs modified

Remove all request.REQUEST usages.

TNL-4136 fix topic detail endpoint's url to support alphanumeric and period characters in topic ID

Allow multiple instances of ccx

Use yaml.safe_load, since we have no need for the greater power of .load

Release

Fix build failures in the docs/en_us/platform_api guide.

Only allow ecommerce checkout if user is also activated

Update translations (autogenerated message)

add student email in credit service

Use latest version of drag and drop xblock

MA-1038

mathjax preview should be inline by default

Release 2016-02-24

Modified permission classes for CCX REST APIs

Modified how the per object permissions are enforced in the CCX REST APIs

User automatically registered to course.

Release Candidate rc/2016-02-23

Adjusted the list of mock modules for the platform API documentation build. This prevents build failures when Sphinx cannot import modules. Addresses https://openedx.atlassian.net/browse/DOC-2638.