Handle playlist of internet radio stations

[ik666]

Added playlist support for handling internet radio stations. No transcoding yet (probably not neccesary for the usual codecs).

Feature can be tested with:

• Generate Radio Browser playlist and copy it to a share (do not place to many radio stations inside playlist file, yet)

my_internet_radio_station.m3u file consists of radio stations like

#EXTM3U

#RADIOBROWSERUUID:962cc6df-0601-11e8-ae97-52543be04c81
#EXTINF:1,Dance Wave!
https://dancewave.online/dance.mp3

• VLC navigating to VLC media player -> Universal Plug 'n Play -> UMS -> my_internet_radio_station.m3u -> radio

Netty 3 MediaServer implementation seems to have an issue serving large chunked streams and becomes more and more unresponsive over some time (a few seconds !).

JDK MediaServer implementation is much more responsive and stable over time. server_engine config entry should therefore be something like 1.

Todo :
[x] cache radio station metadata in a table
[-] currently for for a radio station 2 resources are created, one is VLC Web Audio (probably the renderer) and one is "no transcoding". Maybe this is only cosmetic and can stay this way.
[x] read metadata from radio browser API if possible
[-] adding support for hardware audio player (not in scope any more)

[SurfaceS]

I'm not reviewed the core goal of the PR. Only the Java part and UMS integration.

[SurfaceS]

Tell me if I'm wrong, but I checked the code and I think that the changes in RequestV2 can be completely removed, as the server serve the media url to the client (as it should), so this part is never/should never been reached (and UMS is not a proxy).

For the other part (retrieving media/radio info), we should care that some users do not want that UMS browse the internet (that is why I put this in external).

[ik666]

Tell me if I'm wrong, but I checked the code and I think that the changes in RequestV2 can be completely removed, as the server serve the media url to the client (as it should), so this part is never/should never been reached (and UMS is not a proxy).

If you want the playlists to work as intended, UMS needs to retrieve the data from the external radio station and stream it to the renderer (is kind of a proxy). The stream could also be transcoded if needed. The external URL could of course on top be presented as a res resource in the DIDL result. The control point/renderer should pick the right one (as proposed by the CDS v4 service doc).

For the other part (retrieving media/radio info), we should care that some users do not want that UMS browse the internet (that is why I put this in external).

But: If UMS is not connecting to the internet, it can not serve the radio station. Then this feature won't work.