Ability to trash non-audio streams when updating metadata

File examples:
- http://superjoe.s3.amazonaws.com/temp/eddie-money-home-tonight.m4a
- http://superjoe.s3.amazonaws.com/temp/first-crush-knife-city.mp3

By default we want to preserve all streams when updating metadata. But some files we can decode the main audio stream fine but not preserve all streams when updating. There should be an option to trash all streams other than the main audio stream.