- Setting exterior ring will force all interior rings to match
dimensionality of exterior ring
- add equality operator
- use correct WKB types for rings when creating polygon from WKB
- segmentize curves when setting exterior ring with curved segments
- fix export to GML2/3 (should use LinearRing, not LineString as
ring element tag)
- when creating geometry from WKT, upgrade dimensionality of geometry
if coordinates are 3/4 dimensional
- match dimensionality of collections to child dimensionality
- fix area of curves was non-zero if curve is closed
- don't consider m values when testing for curve closedness
- add unit tests for closedness
- add unit tests for CircularStrings, CompoundCurves, CurvePolygon,
tests with geometries with Z/M values
