Remove VLC_META_ENGINE_*
Don't use VLC_META_INFO_CAT
Avoid using input_Item{Add,Get}Info
Remove disabled code in cdda
Remove "meta fetcher":
    There was only 1 module (not) implementing it (musicbrainz)
    Reduces complexity in playlist core
Use a more consistent naming
Factorize QT4 sorting and column display code
Remove unused members