Fix io_mesh_atomic, utility panel: changing the atom material did not change the material of 'normal' and 'skin' sticks

Reason: a material change of also 'normal' and 'skin' sticks was
simply not included. Recently, it was done for 'dupliverts' sticks
(see https://developer.blender.org/rBA84f5f4699232decc2f1a8694312680b9e5159462)

Now, the atoms and corresponding sticks of any representation ('dupliverts',
'skin' and 'normal) change the material when using the utility 'Change atom shape'
in the 'Utility Panel'.