Created the 'TP02' model target function.
This is the Trott and Palmer 2002 R1rho analytic model for 2-site exchange.
This commit follows step 4 of the relaxation dispersion model addition tutorial (http://thread.gmane.org/gmane.science.nmr.relax.devel/3907).
Authored by: bugman 2013-07-31
Parent: [r20491]
Child: [r20493]
