[airplay] - handle empty session ids from itunes
[airplay] - refactor the playstate announcement by using the IAnnouncer interface
- also adapt to some new findings on revers engineering itunes airplay traffic (add sessioncounter to reverse event and fix http request formatting)
- fixes #14191

Conflicts:

	xbmc/network/AirPlayServer.cpp
Merge pull request #2582 from Memphiz/frodo_airplayconflicts

Frodo airplayconflicts