Play the advertisements before the streams

[michaelarnauts]

We should parse the advertisements, and play a playlist with the advertisements and the main stream.

I don't think there is a way to play the mid-program ads.

This is probably not a popular decision, but we want to do so to keep the add-on in line with the service of Vier/Vijf/Zes.

[mediaminister]

I have an experimental implementation ready: #28

This is an incomplete, minimal implementation, on the website vier.be there are many more "custom params" used to track users and possibly personalize ads.