use png output

src/main/jastadd/common/Tracing.jadd

@@ -18,7 +18,7 @@ aspect Tracing {
           .setNameMethod(o -> o == null ? "null" : o.getClass().getSimpleName())
           .setBackgroundColorMethod(n -> (n == highlightNode ? highlightColor : DEFAULT_COLOR))
           .excludeTokens("Q.") // FIXME remove domain-specific code
-          .dumpAsPNG(de.tudresden.inf.st.mg.common.MotionGrammarConfig.astDiagramDir.resolve("Context-" + worldName + "-" + new java.text.SimpleDateFormat("yyyy.MM.dd.HH.mm.ss.SSS").format(new java.util.Date()) + "-" + step + ".png"));
+          .dumpAsSVG(de.tudresden.inf.st.mg.common.MotionGrammarConfig.astDiagramDir.resolve("Context-" + worldName + "-" + new java.text.SimpleDateFormat("yyyy.MM.dd.HH.mm.ss.SSS").format(new java.util.Date()) + "-" + step + ".svg"));
     } catch (java.io.IOException e) {
       e.printStackTrace();
     }