title: Jenkins plugin shows on Plugin page but does not show on configuration page
body: <p>I am creating a hello world plugin for Jenkins by following <a href="https://blog.codecentric.de/en/2012/08/tutorial-create-a-jenkins-plugin-to-integrate-jenkins-and-nexus-repository/#part1" rel="noreferrer">Tutorial: Create a Jenkins Plugin to integrate Jenkins and Nexus Repository</a>. After I followed the steps, I can run Jenkins and test the plugin.</p>
  
  <p>It shows on Installed Plugin Page.</p>
  
  <p><img src="https://i.stack.imgur.com/ZoK63.png" alt="enter image description here"></p>
  
  <p>Then I go to Configuration page and expect to see <code>Hello World Builder</code> section like the below image, but there is not.
  <img src="https://i.stack.imgur.com/9SV5A.png" alt="enter image description here"></p>
  
  <p>What steps did I miss? Is there anything I have to do before having that plugin show up on the configuration page?</p>
  
  <p><strong>Update</strong>
  This is the project layout, I haven't modified anything on it yet.
  <img src="https://i.stack.imgur.com/mIVOB.png" alt="enter image description here"></p>