rtmp2sink: support EOS event for gracefull connection shutdown
Previously connection was just dropped, now special RTMP commands will be sent first, which makes receiving side aware of the graceful shutdown.
New behavior defaults to sending FCUnpublish
and deleteStream
RTMP commands, which seems to be quite common, but can be reconfigured if necessary.
Thanks to @heftig for help with my first contribution here.
Fixes #1285 (closed)