fix union issues
the data structure of box handle has been changed
the triangles and segments are treated differently from the points,
polygons and volume (there is a presentation available on the topic)

The intensive testing as led to a number of bug identification and fix

[fix union] update all primitive ptrs on merge

[fix union] create an use 3D Polygon with hole

[fix union] attempt with Polygon_3 failed

[fix union] nearly done, replaced the high level

[fix union] a leak remains

[fix union] unit test pass

[fix union] fix segfault

{fix union] styling

[fix union] removed vtk output

[fix union] removed test for NotImplemented
because it is implemented now

[fix union] fix recompose TIN, valid union result

[fix union] fix a special case in difference
when a volume just touches on a point

[fix union] styling

[fix union] fix bug in surface graph
a last fix for union of volumes