title: Template Jenkinsfile for all project
body: <p>For example:</p>
  
  <p>I have 30 multibranch Git projects. All projects have their own Jenkinsfile. And suddenly I find a cool Jenkins plugin which I want to add for all projects. This is pain to do it on all projects and this is a big waste of time.</p>
  
  <p>Is it possible to create somethink like template Jenkinsfile which will be something like wrapper for project Jenkinsfile or somethink like that which gives me possibility to do changes in 1 place instead of 30 places?</p>
  
  <p>What I want is something like that:</p>
  
  <pre><code>stage {
   ...}
  timestamps {
      &lt;include rest of stages definied in projects&gt;
  }
  stage {
  ... }
  </code></pre>
  
  <p>Template file which is in some repo is looked for like this. All of the projects have their own stages defined which are included in the middle of the template Jenkinsfile and defined in project.</p>
  
  <p>So Jenkinsfile in project must:</p>
  
  <ul>
  <li>load template from repository</li>
  <li>put stages in the middle of template Jenkinsfile</li>
  </ul>