Add index worker to Jockey.

[TravisCouture]

Right now Jockey cannot obtain index level information (e.g. all the videos in an index, index name, description, etc.) and this makes if very cumbersome to perform operations across multiple videos in an index an index wide analysis. For the initial index worker we should add the following capabilities.

1. Get index name
2. Get index description
3. Get list of videos in index