Add tracking for YouTube videos #2156

This is a WIP. I'm tracking the following events right now

1. Load event for YouTube videos
2. Play/Paused/Buffering/Finished status of the video
3. Video Quality
4. Errors, reported by YouTube API
5. 10% increments of video played.
We would have to do some content clean-up first. @Elchi3 - is there a way to get a list of all articles that have a YouTube video in them?