Map in Editor: add button to automatically store a screenshot image joined with a location

[laurivesa]

There needs to be a method to store a screenshot (of satellite image or map in the view) as a PNG (or JPG) image. This may require a new property set for a image file.

Alternatively, a screenshot image can be a node for a coordinate data, where an image is associated with a location (point).

A file attribute can be used to store the screenshot; in the props of that attribute we can add the uuid of the linked coordinate attribute; in the location editor, we could add a button to take a screenshot and store it in the associated file attribute (if any).