utilities section and caption update utility

@jbau please take a look.

This is the first draft of the new utilities page (Tools > Utilities) and includes an "update captions" utility. The utility shows all the videos in the course to the user, with an icon indicating whether Studio has the same copy of the video captions as youtube. User can then use the utility to replace caption files with those from youtube.

The functionality to update a single video currently exists in studio. The key idea here is that when professors want to update many videos, they would be able to do it quickly in bulk (rather than updating each video individually).

I'm looking for feedback on both functionality and look and feel of the new pages. Code is still in development and is missing unit tests and needs some clean up.