When an MP3 is only ID3v1 (and album art can't be embedded), provide a shortcut to convert to ID3v2
MP3s with ID3v1 tags cannot have album art embedded. Currently bliss just reports this as a failure. Add a response to the failure activity to upgrade the tag, and insert the art.
This is now completed. When you get presented the error message about ID3v1, you get an option to add an ID3v2 tag and reinstall the artwork, embedding it in the latter tag.