media-db: Add possibilty for meta-data field query
media-db: Add possibilty for meta-data field query

Pelagicore/Media-Manager-Rygel-patched,Pelagicore/Media-Manager-Rygel-patched,Tarnyko/rygel,Tarnyko/rygel,GNOME/rygel,luisbg/rygel,jku/rygel,Pelagicore/Media-Manager-Rygel-patched,GNOME/rygel,GNOME/rygel,jku/rygel