STUD-1726

STUD-1707

Refactor get_parent_locations STUD-1663

rather than have caller figure out whether to call draft or direct.
Fixes get_children to always find draft children in studio.
STUD-1662

This commit adds all of cms.

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]

1.) Making YouTube mock server serve YouTube API.
2.) Adding ability to block YouTube API from YouTube mock server.
3.) Adding acceptance tests that check YouTube mock server for availability of YouTube API, and for it's ability to block YouTube API.

Part of BLD-939.

Student logins to edx, plays video, selects position, closes
browser, opens video, position is restored.

BLD-385

Refactored stub services for style and DRY

Added unit tests for stub implementations

Updated acceptance tests that depend on stubs.

Updated Studio acceptance tests to use YouTube stub server; fixed failing tests in devstack.

Fixing merge conflicts in tests.

Instead of raw comparison against an HTML string to get style information,
now proper selenium function is used to get value of CSS property.