removed default 'a.pdf' output filename, replaced it by undefined (will be generated as filename.pdf from filename.staves -- e.g. foo.staves -> foo.pdf)
added stavesPerPage computation for viewport relations (found that a relation below width/height=1.55 should create 3 staves per page, less should create 2); added filename extraction (foo.staves -> foo.pdf)
added the german traditional 'herbei o ihr gläubigen'
added 0-padded indices to filenames; added minimal stylesheet to generated html