Polygon ear cutting heuristic fix

Within vtkDelaunay2D calls are made to vtkPolygon::Triangulate() to enforce edge constraints. vtkPolygon::Triangulate() is a heuristic ear-cutting method that breaks down under certain circumstances and has no tuning parameters. This MR adds a sequential version of the ear-cutting method to vtkPolygon that contains a tuning parameter (the starting vertex). This degree of freedom is exploited in vtkPolygon::BoundedTriangulate() to test several triangulations and reject those whose smallest-area triangle falls below a user-defined threshold. This more robust (and more costly) ear-cutting method is implemented in vtkDelaunay2D and vtkIntersectionPolyDataFilter.