BLD-662

player.getAvailableQualityLevels returns a non-empty array, it will eventually display, if HD qualities are available (highres, hd1080, hd720). [BLD-937]

"CC button works correctly w/o english transcript in HTML5 mode of Video component"

Fix donwload subs for non youtube videos and non-en language - continue.
Add acceptance tests.
Add detetion of assets on request.
Updated docstring.
Add fixes and acceptance tests.
Fix acceptance tests.
Update docsrtings and cleanup code, resful for language_id.
Specify exception type in POST.
Fix url in upload module.
Improve exception handling.
Remove 'en' and catching in editable_metadata.
Move descriptor.get_context test to lms tests.
Add query parameter to translation dispatch.
Response to format parameter of translatin GET request.
Fix Acceprance test: Metadata Editor.
move handlers to proper scores.
Split video player into smaller files.
Add ugettext and fix typoes.
Add changelog.
Support for downloading non-ascii filenames.
Change event binding.
Add content-language to download requests.
Reractor POST handler to not update self.transcripts.

When the video has both YouTube IDs and HTML5 sources, and
the YouTube API is blocked, then HTML5 sources should be
used.

Check for status in test.
Add test for track url.
Fix test to use cookie.
Use download_track in feature file.
Add new tests for get_transcript.
Add html5 test.
Add content check.
Add tests for available_translations dispatch.
Disable flaky cms test.
Add  w/o english transcript tests.
Add to changelog.

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

BLD-385

Added feedback check for AI-assessment test

Added peer assessment feedback test

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.