title: Set $PROJECT_NAME in docker-compose file
body: <p>I am using the same <code>docker-compose.yml</code> file for multiple projects. I am really lazy, so I don't want to start them with <code>docker-compose -p $PROJECT_NAME up</code>.</p>
  <p><strong>As of Docker version 17.06.0, is it possible to set the variable directly in the <code>docker-compose.yml</code> file?</strong></p>