Consider updating ID3 metadata of enclosure files

[richardcornish]

It's unclear how much Apple uses a file's ID3 metadata, but it is mentioned twice in the documentation under <title> and <itunes:image>, although the use of the word "metadata" in the <title> section is, admittedly, ambiguous.

Some research and testing should be done to examine whether it's a good idea to update an enclosure file's ID3 tags with Mutagen, such as title, author, genre, artwork, etc.