added edge union cases

CMakeLists.txt

include/contourize.h

include/convex_triangulation.h

include/interpolate_z.h

include/orientation.h

include/point.h

include/shift_triangle.h

include/triangle.h

include/triangulation.h

src/data_structures/quad_tree.cpp

src/debug_utilities/mostly_equal.cpp

src/debug_utilities/print_triangles.cpp

src/debug_utilities/shift_triangle.cpp

src/shapes/point.cpp

src/shapes/triangle.cpp

src/union.cpp

src/utilities/contourize.cpp

src/utilities/convex_triangulation.cpp

src/utilities/interpolate_z.cpp

src/utilities/intersections.cpp