Implement DASH support

[Ivan Zderadicka]

I have seen other some audiobooks servers supporting HLS, it looked quite interesting, because it provides new possibilities for streaming.

So I was thinking about DASH as more standard alternative to HLS and possibly have adaptive streams with OPUS codec,.
There has been few articles about OPUS support in DASH, but unfortunately it does not seem to be widely available option yet, so it'll require more research