Implement a queued pre-transcoding

Sometimes, the transcoding job might not be fast enough to keep up with the demand. This means that the only way to play such media in the receiver is to start it and the pause. This presents all manner of problems, mainly possible disconnections after long pauses, and having to wait long periods of time between sequential plays.

The solution is to create a pre-transcoding queue, that automatically starts pretranscoding the media, so when the user wants to start vieweing, the experience is as smooth as possible.