title: sort swift array and keep track of original index
body: <p>I would to sort a swift array and keep track of the original indices.  For example:
  arrayToSort = [1.2, 5.5, 0.7, 1.3]</p>
  
  <p>indexPosition = [0, 1, 2, 3]</p>
  
  <p>sortedArray = [5.5, 1.3, 1.2, 0.7]</p>
  
  <p>indexPosition = [1, 3, 0, 2]</p>
  
  <p>Is there an easy way of doing this?</p>