tracker-extract-mp3.c: Extract MusicBrainz IDs for mp3 files
Tracker needs to store MusicBrainz IDs to allow retrieval of tags and cover-art in GNOME Music. If a file already has MusicBrainz IDs, then extractor should detect and index them. Extraction of MusicBrainz IDs is done based on tags used by Picard.
Closes #68 (closed)