title: how to use variables and import files in symfony yaml config component
body: <p>I use the config component of symfony on a project and I need tu use the same value in various sections of my yml configuration file.</p>
  
  <p>Does someone know how to reproduce the behavior of the symfony configuration.yml using the config component?</p>
  
  <p>I would like to import configuration files:</p>
  
  <pre><code>imports:
    - { resource: otherfile.yml }
  </code></pre>
  
  <p>or to declare variables:</p>
  
  <pre><code>myvar: value
  othervar: %myvar%
  </code></pre>