allow break paged output

* compatibilty to Liederbuchgenerator
* apply standalone output directly to top level not wrapped in a book

break_paged_output.ily

@@ -0,0 +1,2 @@
+\include "lilypond-book-preamble.ly"
+#(ly:set-option 'separate-page-formats "pdf")

standalone_output.ly

@@ -18,19 +18,19 @@ TEXT = \markuplist {
   \TEXT
 }
 
-% nur Output wenn noStandaloneOutput auf false steht
-output = #(if (not noStandaloneOutput)
-#{
-  \bookpart {
-    \HEADER
-
+#(if (not noStandaloneOutput)
+(begin
+  (let ((header (ly:book-header HEADER)) (paper (ly:book-paper HEADER)))
+    (if header (set! $defaultheader header))
+    (if paper (set! $defaultpaper paper))
+  )
+  (add-score #{
     \score {
       \MUSIC
       \layout { \LAYOUT }
-    }
-
-    \TEXT
-
+    }#})
+  (add-score TEXT)
+  (add-score #{
     \score {
       \unfoldRepeats { \MUSIC \INLINESCOREMUSIC }
       \midi {
@@ -40,15 +40,5 @@ output = #(if (not noStandaloneOutput)
           tempoWholesPerMinute = #(ly:make-moment midiQuarterNoteSpeed 4)
         }
       }
-    }
-
-
-  }
-#}
-)
-
-% if we don't want a standalone output, cause we compile a book, we just have an empty output here,
-% so lilypond does not generate output for this song
-\book {
-  \bookpart { \output }
-}
+    }#})
+))