Add files required to print callouts in html format.
    
    - Previously, when you html files were produced, there wasn't any
      image path nor image files for callouts. As consequence, callouts
      weren't printed as expected. This update adds the SVGZ files and the
      render.conf file needed to produce callouts PNG images. This update
      also changes the related Xsl files to set the correct path of
      callout images. Now, callout images are printed as expected in html
      documents, produced from render module.