title: Copy constructor using "initWith" for "productFlavors" and "sourceSets"
body: <p>With reference to <a href="https://stackoverflow.com/a/34111442/1957401">this answer</a>. Is it possible to create a copy constructor for <code>productFlavors</code> and <code>sourceSets</code> using <code>initWith</code> just like the one in the linked answer. That one worked great for <code>buildTypes</code>.</p>
  
  <p>For <code>buildTypes</code> it was done this way:</p>
  
  <pre><code>debugfree.initWith(buildTypes.debug)
  </code></pre>
  
  <p>Is this possible for <code>productFlavors</code> and <code>sourceSets</code> as well?</p>