RemoteViewsTarget feature requested on #242

Ability to load a bitmap into an ImageView of a Widget using
RemoteViews.

Example of usage on the following gist
https://gist.github.com/pavlospt/00242d5102ac8f76e169
I've just written a widget, and my update function is complex, and it updates each widget on it's own. In your gist you're sending the same image to ALL of your widgets on the screen.

Check this code:
```
for (int appWidgetId : appWidgetIds) {
    String url = determineUrlFrom(appWidgetId); // e.g. read from preferences and then build a specific url string
    RemoteViews remoteViews = new RemoteViews(...); // each widget may have a different layout
    RemoteViewsTarget target = new RemoteViewsTarget(remoteViews, context, R.id.iv_id, 100, 100, appWidgetId);
    Glide.with(context).load(url).asBitmap().into(target);
}
```

My point being here is that with the current implementation I would have to create an int[]:
```
new RemoteViewsTarget(remoteViews, context, R.id.iv_id, 100, 100, new int[] { appWidgetId });
```
which could be easily done automatically by the compiler if you've used `int... widgetIds` which is equivalent, but more flexible to `int[] widgetIds`. Also that array/... should be `@NonNull` because if there are no ids, there's no point in having the target at all, it'll just fail with NPE later.