Added support for optimising the 'LM63 3-site' dispersion model with Art Palmer's CPMGFit.
This is for the relax_disp.cpmgfit_input user function. This model in CPMGFit is called '3-site_CPMG'.
Authored by: bugman 2013-07-19
Parent: [r20418]
Child: [r20420]
