Authoring tool: add a label in Step 2 to help non-SoundCloud audio

[JoeGermuska]

When adding a second non-SoundCloud clip from a different audio source, it's hard to be confident that the authoring tool has loaded the new sound because there's no label.

Can we read the ID3 metadata from the file after it's loaded? If so, we should use that. If not, we could get by with the URL, or maybe even just the file part of the URL.