[airplay] - ensure to announce airtunes before airplay via zeroconf (makes it more likely that ios7 clients detect us correctly at the first shot)
[zeroconf] - add method to reannounce already published services
[airplay] - reannounce airplay service every 10 secs (fixes ios7 clients not detecting us when their wlan was asleep or they saw the airplay announcement before the airtunes annoncement)
[airplay] - fix regression introduced by ios7 clients by Memphiz

This is the fix for the fix https://github.com/xbmc/xbmc/pull/4414
Thought I would pull this in rather than wait for the merge as it works
fine now.