title: Remove background from ImageCardView
body: <p>I started using new <code>android.support.v17.leanback</code> library and have some trouble in styling <code>ImageCardView</code>. </p>
  
  <p>I am changing the image on <code>ImageCardView</code> to have a different shape so I would like to remove background and shadow which are automatically generated when using the card in <code>ListRow</code> for example. If I leave the shadow, my card looks weird because shadow and background are showing like the card is square.</p>
  
  <p>I've tried to set the different background to all the elements but it doesn't work. If I set the normal background color (green, blue, etc), the background of the image or info area would change but if I set the transparent background, another background which wraps the whole card would be visible.</p>
  
  <p>Any ideas how to solve this issue?</p>