Fix - skip orphans from content group usage information for split

Refactor Block Cache to separate Collect and Transform phases

Refactor js_util helpers

- Rename escape_json_dumps to dump_js_escaped_json
- Rename escape_js_string to js_escaped_string
- Update js_escaped_string to output empty string for None
- Introduce dump_html_escaped_json
- Move dump_js_escaped_json after the pipe as new best practice
- Introduce additional uses of helpers
- Introduce new djangolib directory and move js_utils

MA-1368

Remove skip from studio page bok choy test

Course home page improvements.

Fix unit tests so they are testing aria-expanded.

Events are added for accessing the courseware, entering the verified
upgrade flow, and toggling a course update.

ECOM-2983

ECOM-2960

This reverts commit e8909e4439f22a7568d95a7672ab60d4a36f7322.

ECOM-2809

The existing course handouts section is moved underneath Course
Updates and News, with updated styling.

ECOM-2808

ECOM-2806

lms: Only show welcome video if show_homepage_promo_video is set

Bump edx-proctoring to 0.12.8

ECOM-2678

ECOM-2810

Merge pull request #11383 from edx/rc/2016-02-02

CMS: Removing H1 and H2 from editor options; updating editor icons

Be specific about JS files for cms-squire.

Add xseries certificates sidebar section in edx.org theme

As required by CONTRIBUTING.rst.

While show_homepage_promo_video would previously toggle the control to
play the welcome video on and off, the YouTube embed iframe would be
included in index.html unconditionally. This created the ugly
situation that YouTube would try to pull in a non-existent video, and
that a DoubleClick tracking beacon would be introduced to the start
page for no reason.

Instead, make sure show_homepage_promo_video toggles the entire modal
video section on and off, suppressing it altogether unless
show_homepage_promo_video is set.

ziafazal/WL-305: removed constraints on MicrositeHistory model to allow Updates on Microsite

Convert PARTNER_SUPPORT_EMAIL to a setting.

Release Candidate rc/2016-02-02