title: BackgroundImage when using MasterDetailPage
body: <p>I have a ContentPage, such like this:</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
      xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
      x:Class="XXXXXX"
      Title="Title"
      BackgroundImage="bg_app.png"
      Padding="5"&gt;
  </code></pre>
  
  <p>When I use that page directly in App.Current.MainPage the BackgroundImage appears... But, when I use the same page in MasterDetailPage.Detail, the background image don't works...</p>
  
  <p>When I set MasterDetailPage.BackgroundImage property... The BackgroundImage don't work too.</p>
  
  <p>Any sugestions?</p>