[TIMOB-6378] Ti API: Default background color for views is inconsistent

The following code produces different effects on Android and iOS:

var view = Ti.UI.createView({
  width: 200,
  height: 200,
  borderColor: '#c00',
  borderWidth: 1
});

win.add(view);

On iOS, this produces a transparent box with a red border. On Android, it produces a solid red box. The workaround is simple enough--specify a background color. But the result is puzzling to customers, who are more likely to expect the iOS behavior. Reported in Stack Overflow: http://stackoverflow.com/questions/8222159/titanium-android-bordercolor-behaving-like-backgroundcolor