Remove some outdated code.
Opaque-keys: fix pep8 violations
Opaque-keys: fix pylint violations
StaffFactories accept `course_key`s, not `course`s. Make that clear in the interface.
Fixed some TODOs, removed irrelevant ones
Merge pull request #3861 from edx/sarina/fix-quality

Fix quality violations from opaque-keys
Refactor video volume control.
i18n: More extractable & localizable strings in xmodules
Merge pull request #3678 from edx/anton/refactor-volume-control

Video: refactor volume control.
Merge pull request #3878 from louyihua/master

i18n: More extractable & localizable strings in xmodules
i18n: Make XBlock buttons & components have localizable display names

1. Current code uses type name as the display names for XBlock buttons, so the name of these five buttons can't be localized. This fix contains code that adds a 'display_name' field for the buttons, and makes their names localizable.
2. The display names of components in advanced, html and problem types can be localized now.
i18n: Fix an i18n string extraction error in 02_html5_video.js

Replace a string concation to a single string to prevent the partial extraction of the string.
BLD-967: Fix regExp.
Bok-Choy Tests for Video Start Time, End Time and Finish Time
Merge pull request #3883 from edx/anton/fix-youtube-regexp

Fix youtube regular expression in video player editor
BLD-975: Remove Video player outline.
Merge pull request #3694 from edx/ammar/bok-choy-video-time-tests

Bok-Choy Video Time Tests
Merge pull request #3876 from louyihua/localization-fix-video

i18n: Fix an i18n string extraction problem in 02_html5_video.js
Merge pull request #3877 from louyihua/translation-fix-cms

i18n: Make XBlock buttons & components have localizable display names
Merge pull request #3886 from edx/diana/clean-up-outdated-files

Remove some outdated code.