[TIMOB-20586] Parity: backgroundColor, backgroundImage, backgroundGradient

   var window = Ti.UI.createWindow(
       { title: 'TIMOB-20586' }
   );
   //backgroundImage:"images/back.jpg" for android.
   //backgroundImage: "back.jpg" for ios.
   //common path is assets/images/back.jpg
   var view = Ti.UI.createView({
       backgroundColor: 'yellow',
       backgroundGradient: {
           type: 'linear',
           startPoint:
           { x: '0%', y: '50%' }
           ,
           endPoint:
           { x: '100%', y: '50%' }
           ,
           colors: [
               { color: 'red', offset: 0.0}
               ,
               { color: 'blue', offset: 0.25 }
               ,
               { color: 'red', offset: 1.0 }
           ]
       },
       backgroundImage: 'assets/images/back.jpg'
   });
   window.add(view);
   window.open();
   //
   try {
   	var file = Titanium.Filesystem.getFile("assets/images/back.jpg");
   	console.log("The file assets/images/back.jpg exists: " + file.exists());
   } catch (err) {
   	console.log("The file was not retrieved");
   }