Add albumArtURI to MusicTrack didl_properties_defs#45

StevenLooman merged 2 commits intoStevenLooman:masterStevenLooman/python-didl-lite:masterfrom

RicterZ:fix/music-track-album-art-uriRicterZ/python-didl-lite:fix/music-track-album-art-uriCopy head branch name to clipboard