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.
Now that we have FeatureId support (see #733), we can add this back to the
GML parsers (v2 and v3). Also add write support for FeatureId in KML, read
support was already added by @fredj
This adds a parser (read/write) for GML v2 and v3. GML v3 is limited to the
simple features profile of GML 3.1.1, just like OpenLayers 2 was. This will
be the basis for the WFS parser, but it only makes sense to continue this work
once feature modification (insert, update, delete) is in place in ol3. So the
WFS parser will be another pull request.
