UPnP: Expose more metadata to UPnP clients

A lot of upnp clients won't use it, but it's there for those that do.

For recordings:
channelID
channelName
callSign
channelNr
seriesTitle
programTitle
episodeNumber*
episodeCount*
recordedStartDateTime
recordedDayOfWeek
seriesID
programID
srsRecordScheduleID

For videos:
seriesTitle
programTitle
episodeNumber*

For music:
playbackCount
lastPlaybackTime

*These likely expect the value to be for the entire series rather than
 per-season since there is no provision for season ID. However since
 it's not that specific we populate them with the episode number
 within a season.