Internationalize the video player.

[BLD-699](https://edx-wiki.atlassian.net/browse/BLD-699).

Needs to make sure that all the English text presented to the user are properly marked for internationalization.

Checked files:
  - common/lib/xmodule/xmodule/js/src/video/01_initialize.js;
  - common/lib/xmodule/xmodule/js/src/video/025_focus_grabber.js;
  - common/lib/xmodule/xmodule/js/src/video/04_video_control.js;
  - common/lib/xmodule/xmodule/js/src/video/05_video_quality_control.js;
  - common/lib/xmodule/xmodule/js/src/video/06_video_progress_slider.js;
  - common/lib/xmodule/xmodule/js/src/video/07_video_volume_control.js;
  - common/lib/xmodule/xmodule/js/src/video/08_video_speed_control.js;
  - common/lib/xmodule/xmodule/js/src/video/09_video_caption.js;
  - common/lib/xmodule/xmodule/video_module.py;
  - lms/templates/video.html;
  - cms/djangoapps/contentstore/views/transcripts_ajax.py;
  - cms/djangoapps/contentstore/transcripts_utils.py;
  - cms/templates/js/transcripts/metadata-videolist-entry.underscore;
  - cms/templates/js/transcripts/file-upload.underscore;
  - cms/templates/js/transcripts/messages/transcripts-choose.underscore;
  - cms/templates/js/transcripts/messages/transcripts-found.underscore;
  - cms/templates/js/transcripts/messages/transcripts-import.underscore;
  - cms/templates/js/transcripts/messages/transcripts-not-found.underscore;
  - cms/templates/js/transcripts/messages/transcripts-replace.underscore;
  - cms/templates/js/transcripts/messages/transcripts-uploaded.underscore;
  - cms/templates/js/transcripts/messages/transcripts-use-existing.underscore;
  - cms/templates/widgets/video/transcripts.html;
  - /cms/static/js/views/transcripts/editor.js;
  - /cms/static/js/views/transcripts/file_uploader.js;
  - /cms/static/js/views/transcripts/message_manager.js;
  - /cms/static/js/views/transcripts/metadata_videolist.js;
  - /cms/static/js/views/transcripts/utils.js.

@jmclaus , @olmar please review.