title: count numbers in array and order them by count in swift
body: <p>Is there a easy way to sort an array by the count of numbers? And if a number have the same count put the highest number first.</p>
  
  <pre><code>[2,8,2,6,1,8,2,6,6] 
  to
  [6,6,6,2,2,2,8,8,1]
  </code></pre>