Renamed Contour.SimplifiedVertex to Countour.Vertex
ContourSet now implements ICollection<Contour>
Moved part of ContourSet ctor to a new Contour ctor
Moved CompactHeightfield.CalcAreaofPolygon2D to Contour.Area2D
Refactored some PathfinderCommon constants to PolygonType
Moved NavMeshDetail.VectorCross2D to Vector3Extensions.Cross2D
Moved PathfinderCommon.TriangleArea2D to Triangle3.Area2D
Renamed Poly.GetType() to GetPolyType() to avoid hiding object.GetType()