- deprecate the following function 
Classification_type   	  A.classify ( Cell_handle f, int i, FT alpha = get_alpha())
because it is ambiguous with
Classification_type   	  A.classify ( Cell_handle f, FT alpha = get_alpha())
when alpha is given as an int.

- Get rid of the derivation from Triangulation_3
  add a Triangulation_3 as a data member 
  creators from a triangulation:
  Alpha_shape_3(cnst Dt& dt, NT alpha = 0, Mode m = REGULARIZED)
  The triangulation is copied
  Alpha_shape_3(Dt& dt, bool swap=true, NT alpha = 0, Mode m = REGULARIZED)
  The triangulation is swapped  if swap=true and copied otherwise.

- test the taking into account of parameter alpha in functions
get_alpha_shape_edges
get_alpha_shape_facets
get_alpha_shape_vertices
get_alpha_shape_cells