indexer: basic logging
indexer: indexing of scores with undefined id fixed

previously the chunk files would overwrite each other resulting in many Chants
having the same image path - where the last processed one would be found
introduced specs; fixed bug in the last fix of the indexer :) found thanks to the spec
indexer: interpunction stripped from the 'machine lyrics'
piece detail: show both readable and normalized lyrics
use the same lyrics normalization function in Indexer and Decorator