add configure page

src/main/java/org/codefirst/jenkins/wsnotifier/WsNotifier.java

@@ -36,6 +36,9 @@ public DescriptorImpl getDescriptor() {
 
     @Extension // This indicates to Jenkins that this is an implementation of an extension point.
     public static final class DescriptorImpl extends BuildStepDescriptor<Publisher> {
+        private int port = 8081;
+
+        public int port(){ return port; }
         public boolean isApplicable(Class<? extends AbstractProject> aClass) {
             // Indicates that this builder can be used with all kinds of project types
             return true;
@@ -47,8 +50,9 @@ public String getDisplayName() {
 
         @Override
         public boolean configure(StaplerRequest req, JSONObject formData) throws FormException {
+            port = formData.getInt("port");
+            save();
             return super.configure(req,formData);
         }
     }
 }
-

src/main/resources/org/codefirst/jenkins/wsnotifier/WsNotifier/global.jelly

@@ -0,0 +1,9 @@
+<j:jelly xmlns:j="jelly:core" xmlns:st="jelly:stapler" xmlns:d="jelly:define" xmlns:l="/lib/layout" xmlns:t="/lib/hudson" xmlns:f="/lib/form">
+  <f:section title="Websocket Notifier">
+    <f:entry title="Port"
+      description="Port number of Websocket server"
+      help="/plugin/wsnotifier/help-globalConfig.html">
+      <f:textbox name="port" value="${descriptor.port()}" />
+    </f:entry>
+  </f:section>
+</j:jelly>