title: Scala nested arrays flattening
body: <p>How to flatten an array of nested arrays of any depth ?</p>
  
  <p>For instance</p>
  
  <pre><code>val in = Array( 1, Array(2,3), 4, Array(Array(5)) )
  </code></pre>
  
  <p>would be flattened onto</p>
  
  <pre><code>val out = Array(1,2,3,4,5)
  </code></pre>
  
  <p>Thanks in Advance.</p>