Prioritize MP4 movies using x264 to avoid transcoding

[AaronO]

This is quite an important improvement, since it would reduce CPU and power consumption by avoiding having to convert the movie.

Most movies are available as MP4's with the x264 video codec, which Chrome supports, so it would be a good idea supporting this and falling back to converting the video only if necessary.

This would involve two things :

• Ranking x264 torrents first
• Skip the transcoding in the streaming api endpoint if the current movie doesn't need to be converted