Revert "Merge branch 'poc-diagrams-extra'"

I will replace it with the final version, i.e. not just a
proof-of-concept.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

layouts/diagram-list.html

@@ -1,7 +1,7 @@
 <pre>
-{{ range .Site.Pages -}}
+{{- range .Site.RegularPages -}}
   {{- if in .RawContent "{{< graphviz" -}}
-     public{{ .Path }}.html{{ "\n" -}}
-  {{- end -}}
-{{- end -}}
+    public{{ .Path }}.html
+  {{- end }}
+{{ end -}}
 </pre>