refactored ModuleRegistry to singleton system

Signed-off-by: Stephan Richter <s.richter@srsoftware.de>

markdown/src/main/java/de/srsoftware/umbrella/markdown/MarkdownApi.java

@@ -2,6 +2,7 @@
 package de.srsoftware.umbrella.markdown;
 
 import static de.srsoftware.tools.MimeType.MIME_HTML;
+import static de.srsoftware.umbrella.core.ModuleRegistry.userService;
 
 import com.sun.net.httpserver.HttpExchange;
 import de.srsoftware.tools.Path;
@@ -18,8 +19,9 @@ import java.util.Optional;
 public class MarkdownApi extends BaseHandler implements MarkdownService {
 
 
-	public MarkdownApi(ModuleRegistry registry) {
-		super(registry);
+	public MarkdownApi() {
+		super();
+		ModuleRegistry.add(this);
 	}
 
 	@Override