import subtitles into studio: add python side functionality
import subtitles into studio: add python integration tests
import subtitles into studio: add python unit tests for utils functions
Added button in Studio editor for Subtitles interface.
Rework of adding button to Studio edit dialog. Now general to any xmodule.
Change tabs js logic
Add import from YT
upload subtitles into studio: add python side functionality
upload subtitles into studio: add python integration tests
upload subtitles into studio: add python unit tests for utils
Add upload subtitles file + Refactoring