upnp: serialize/deserialize datetime values in W3C format
upnp: improve metadata (artists, albums) for musicvideos
upnp: include musicvideos in list of video items
upnp: improve streamdetails
upnp: only set the year from the date if the date is valid
upnp: add support for reading actors
Merge pull request #5144 from Montellese/upnp_small_improvements

UPnP: improved metadata