Added basic jenkins conf demo

demos/jenkins/README.md

@@ -0,0 +1,17 @@
+# configure jenkins
+
+Basic Jenkins configuration, which is not a part of any plugin
+
+## sample configuration
+
+```yaml
+jenkins:
+  systemMessage: "Jenkins configured automatically by Jenkins Configuration as Code Plugin\n\n"
+  numExecutors: 5
+  scmCheckoutRetryCount: 2
+  mode: NORMAL
+  scmCheckoutRetryCount: 4
+```
+
+# implementation note  
+Example above is only a subset of commonly used settings, full list available in generated documentation

src/main/java/org/jenkinsci/plugins/casc/RootElementConfigurator.java

@@ -33,6 +33,9 @@ public interface RootElementConfigurator {
             }
         }
 
+        for (RootElementConfigurator c: configurators)
+            System.out.println("[Configurator] " + c.getName());
+
         return configurators;
     }