Update DASH-IF livesim URLs (#1736)
Update DASH-IF livesim URLs (#1736)

 - Changed livesim assets to new host URLs https://livesim.dashif.org.
 - Added SegmentTimeline with $Number$ in addition to SegmentTimeline with $Time$.
 - Added startOver URLS: interval [-20s, 20s] compared to wall-clock. These turn into static at interval end.
 - Corrected some information.
tvoli/shaka-player,tvoli/shaka-player,tvoli/shaka-player,tvoli/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player,shaka-project/shaka-player