artist feature completed.
if no artist name is present in ID3v tags, it tries to get info using
title and/or album.
Merge pull request #3 from AntonioCollarino/mb

artist done.
fixed bug in artist. Added custom event handler for marshaller
partial implementation of album feature.
Merge pull request #4 from AntonioCollarino/mb

Album feature
Created HighLevelSongFeature, fixed songHighLevel.xsd