Add method to determine winding order of linear rings
Store rings so exerior is clockwise and interior is counter-clockwise

KML and WKT don't specify a winding order, so we write those out in CW/CCW order (for exterior/interior).  GML references ISO 19107 that specifies CCW/CW, so we serialize in that winding order.

Having hand generated all this GML data the first time around, I reserve the right to modify it for the tests.
Doc typo
Merge pull request #809 from tschaub/clockwise

Consistent winding order for polygon rings.