Added: (preliminary) Attachment Renaming

At John's request, files are now renamed according to the metadata associated with the parent piece/movement.

Problems:
1) Old filenames may be completely useless, or have valuable information in them that are not otherwise in the piece/movement metadata.
2) Some pieces have very unwieldy names... and special characters that may need escaping
3) Piece names and composer names are named very unsystematically.