Exposed map widget width and height to settings

[RaddishIoW]

I've exposed the map widget attributes for the width and height in the settings, with the defaults set to the same as the original attrs. This way, the user can override the attrs to set the width and height of the map view.

[javiermatos]

Is there any chance to get this merged? I would like to customize widget sizes and this PR is just implementing the feature.