extract meta data from lilypond compilation

* write that as yaml file next to the other outputs
* extract lyrics
* makes chordpro export work in songbooks
* more metadata for chordpro export

private_includes/base/all.ily

@@ -20,7 +20,8 @@
       "scm" file-name-separator-string filename
     )))))
     (scm-load "resolve_inherits.scm")
-    (scm-load "yaml_parser.scm")))
+    (scm-load "yaml_parser.scm")
+    (scm-load "yaml_writer.scm")))
 
 #(define (song-includes-data-path filename)
   (string-join
@@ -39,6 +40,7 @@
 \include "title_with_category_images.ily"
 \include "chord_settings.ily"
 \include "chordpro.ily"
+\include "data_extractor.ily"
 \include "transposition.ily"
 \include "markup_tag_groups_hack.ily"
 \include "verses_with_chords.ily"