some cleanups and album-art support
some cleanups and album-art support

sreichholf/python-coherence,unintended/Cohen,furbrain/Coherence,furbrain/Coherence,coherence-project/Coherence,ismaelgaudioso/Coherence,coherence-project/Coherence,opendreambox/python-coherence,opendreambox/python-coherence,unintended/Cohen,sreichholf/python-coherence,ismaelgaudioso/Coherence