Add 'skip if unavailable' option for streams in playlist

In case a playlist contains a 2 minute live video stream, and the stream is not available - showing 'The stream is currently not available' for 2 minutes may just cause people to stop watching the screen and thereby missing the contents in the rest of the playlist. Likewise, I use netradio stations as background audio for some layouts, but if the stream is dead, it would be preferable if the next item in the audio playlist would automatically start.