Moved the 'spin_id = generate_spin_id(res_num=res_num, spin_name=X_name)' instance into the
different intensity_*() functions.
This is as suggested in a thread started by Edward at:
https://mail.gna.org/public/relax-devel/2008-12/msg00018.html
(Message-id: <7f080ed10812040706v3fadaa2eh2f475aa4ab611da7@...>)
