Fix widget image and add status message

In our Hackerspace, we have multiple open/closed modes, like 'open for public' and 'members only' for which we use the message field in the SpaceAPI. So, if provided, this message should also be shown on the widget.

If there is a TextView on the bottom the widget, the ImageView wouldn't get centered, which looked weird. Also, the provided button background which would cause the ImageView paint a grey border around the image.