relax SVN archive

The code of the specific_analyses.frame_order.geometric.create_geometric_rep() function has been
spun out into 3 new functions: add_rotors(), add_axes(), and add_cones(). This is to better isolate
the various elements to allow for better control. Each function now adds the atoms for its
geometric representation to a separate molecule called 'axes' or 'cones'. The add_rotors() does not
create a molecule as the lib.structure.represent.rotor.rotor_pdb() function creates its own. As
part of the rafactorisation, the neg_cone flag has been eliminated.