Android: fix swiping

[llostris]

1. Enable paging on the scrollview to make sure swiping on Android moves image by image (currently it scrolls continuously, resulting in stopping mid-image)
2. Update page indicator when swiping on Android (currently it doesn't update at all when swiping)

Fixes #haqiqiw/issues/9 (a bug in the original library), using the solution provided in that issue.

[ajithes111]

The issues doesn't seem to be resolved. I'm still having these issues.

[edoantonioco]

pageindicator still doesnt update

[maryaibtissem]

You can add this to solve the problem of pageindicator
<ScrollView
ref={ref => this._onRef(ref)}
........
.......
+ onMomentumScrollEnd={Platform.OS === 'android' && this._onMomentumScrollEnd}

_onMomentumScrollEnd = ({ nativeEvent }: any) => {
let viewSize = nativeEvent.layoutMeasurement;
const index = Math.round(nativeEvent.contentOffset.x / viewSize.width);
if (index !== this.state.currentIndex) {
this._move(index);
}
};

[Keshavdulal]

@kamalpandey could you please review this PR and merge it whenever you are free. I am also facing the exact same issue.

Thanks. :)