This commit implements STUD-1490, allowing creation of components
on the container page. It also enables the delete and duplicate
buttons now that new content can be created that would benefit.
Note that it also creates shared functionality for adding components,
and refactors the unit page to use it too.
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.
