write does not necesserily respect shapefile winding spec

[rafaqz]

We are currently just calling getring and assuming they have the correct winding. Which will often not be true.

Probably a pretty serious bug.

I guess we need to detect the winding order of each ring in _get_parts for holes and exteriors separately, and then iterate either forwards or in reverse over the points depending.

[rafaqz]

We already have _isclockwise here we just need to run it on every ring as we stream the write, flipping the order we do GI.getpoint depending on the current order and if we need a hole or exterior. Maybe only a few extra lines.