Mastrly Player

Open a delivery by scanning its QR code, as well as by pasting a link. A download that gets interrupted now picks up where it stopped instead of starting over, so a large master finishes even on a patchy connection. A delivery whose files are no longer available now tells you so, rather than failing quietly. Songs delivered in several versions now start on v1, and switching between versions is seamless. Various fixes to loading and playback.