Fixed a newly introduced bug in the reading of Sparky peak intensities.
The bug was caused by r2798 (https://mail.gna.org/public/relax-commits/2006-11/msg00096.html). The
expected proton and heteronucleus names returned by the 'self.intensit_xxxxx()' functions had been
swapped but the Sparky intensity function had not been updated.
