[TIMOB-16635] NSURLConnection: Download data to file if specified

   var win = Ti.UI.createWindow({
   	backgroundColor: '#CCC'
   });
   
   var btn = Ti.UI.createButton({
   	title: 'here',
   	top: 10
   });
   
   win.add(btn);
   
   var img = Ti.UI.createImageView({
   	top: 75, bottom: 20,
   	left: 20, right: 20
   });
   win.add(img);	
   
   win.open();
   
   
   btn.addEventListener('click', function(){
   
   	var file = Ti.Filesystem.getFile(Ti.Filesystem.applicationDataDirectory, 'my_file.jpg');
   	var xhr = Ti.Network.createHTTPClient();
   	xhr.file = file;
   	xhr.onload = function(){
   		img.image = file.read();
   	};
   	xhr.onerror = function(){
   		alert('error')
   	};
   	xhr.open('GET', 'http://upload.wikimedia.org/wikipedia/commons/3/3f/Fronalpstock_big.jpg');
   	xhr.send();
   });