[TIMOB-1124] Android: Add support for backgroundGradient on views

var win = Ti.UI.createWindow({backgroundColor: 'black'});

var linearGradient = Ti.UI.createView({
    top: 10,
    width: 100,
    height: 100,
    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 } ]
    }
});
win.add(linearGradient);

win.open();