Test parsing of id3v2.* metadata
Always parse track numbers as base 10
Test extended header support
Fix extended header support for id3v2.4
Test id3 unsynchronization
Support unsynchronized id3 tags
Test multivalue tags
Support multi-value tags for id3
(Optional commit) Stop using "tag" to describe individual metadata fields. An ID3 tag is *all* the metadata; a frame is a single field.