allow embedd fonts from jar-file for pdf creation

fonts can now added in fop configuration via classpath notation. Also added FreeSans.ttf

library/src/main/java/org/mustangproject/ZUGFeRD/ZUGFeRDVisualizer.java

@@ -21,6 +21,7 @@
 package org.mustangproject.ZUGFeRD;
 
 import org.apache.fop.apps.*;
+import org.apache.fop.apps.io.ResourceResolverFactory;
 import org.apache.fop.configuration.Configuration;
 import org.apache.fop.configuration.ConfigurationException;
 import org.apache.fop.configuration.DefaultConfigurationBuilder;
@@ -304,6 +305,11 @@ public class ZUGFeRDVisualizer {
 
 		FopFactory fopFactory = builder.build();//FopFactory.newInstance(new File("c:\\Users\\jstaerk\\temp\\fop-config.xconf"));
 
+		fopFactory.getFontManager().setResourceResolver(
+			ResourceResolverFactory.createInternalResourceResolver(
+				new File(".").toURI(),
+				 new ClasspathResolverURIAdapter()));
+
 		FOUserAgent userAgent = fopFactory.newFOUserAgent();
 
 		userAgent.getRendererOptions().put("pdf-a-mode", "PDF/A-1b");

library/src/main/resources/fop-config.xconf

@@ -25,7 +25,7 @@
    <renderer mime="application/pdf">
    <fonts><!-- https://xmlgraphics.apache.org/fop/1.1/fonts.html auto-embed -->
        <auto-detect/>
-       <font kerning="no" embed-url="FreeSans.ttf" embedding-mode="subset">
+       <font kerning="no" embed-url="classpath:FreeSans.ttf" embedding-mode="subset">
            <font-triplet name="SourceSerifPro" style="normal" weight="normal" />
            <font-triplet name="Times-Bold" style="normal" weight="normal" />
        </font>