title: GestureRecognizers doesnt work on Image but on StackLayout
body: <p>Please someone tell me why this markup doesn't fire the tap gesture?</p>
  
  <p><strong>Not working</strong></p>
  
  <pre><code>&lt;Image.GestureRecognizers&gt;
      &lt;TapGestureRecognizer Tapped="TapGestureRecognizer_Tapped" NumberOfTapsRequired="1" /&gt;
  &lt;/Image.GestureRecognizers&gt;
  </code></pre>
  
  <p>But this one does? And I did followed a very basic implementation from the Microsoft/Xamarin docs on how to add a <code>GestureRecognizer</code>.
  If I switch to this markup it works perfect! Everything tested on  Android phone 7.0 API 24. I use the latest Xamarin.Forms 3.3.0 pre 3 nuget package.</p>
  
  <p><strong>Working Markup</strong></p>
  
  <pre><code>&lt;StackLayout.GestureRecognizers&gt;
      &lt;TapGestureRecognizer Tapped="TapGestureRecognizer_Tapped"  NumberOfTapsRequired="1" /&gt;
  &lt;/StackLayout.GestureRecognizers&gt;
  </code></pre>