title: Is there any version of Angular Material md-select with select all option
body: <p>I have been using Angular Material in one of my project. Suddenly I realized the need for having a select all option on md-select. I think I will pull a git request for the same.</p>
  
  <p>However, currently I am looking for a similar drop down structure with checkboxes (like md-select multiple) but also a select all option.</p>
  
  <p><strong>I am aware that I can push a dummy empty entry into md-select option array and manipulate reverse way on its selection. But it would require a lot of code change in my current structure and would also not be a elegant thing to do.</strong></p>
  
  <p>I tried looking for it in bootstrap and jQuery-UI, but could not find one yet. Is there any such control known to anyone. Any redirection will be helpful. </p>