use right-hand rule for metadata geometry definitions

[johntruckenbrodt]

According to the GeoJSON specification, the outer rings of (multi)-polygons should follow the right-hand rule. I.e., its coordinates should be defined counter-clockwise. See specification section 3.1.6.
Currently the geometry is defined clockwise. This should be changed.

The GML standard allows both conventions. For the sake of simplicity the right-hand rule should be applied to the GML definition in the XML metadata files as well.

Function to be changed: metadata.extract.geometry_from_vec.