Updated the relax_disp.exp_type user function for the new 'MQ CPMG' and 'MQ R1rho' experiment types.
This is needed for the 'MQ NS CPMG 2-site' model.
This follows the tutorial for adding relaxation dispersion models at:
http://wiki.nmr-relax.com/Tutorial_for_adding_relaxation_dispersion_models_to_relax#Creating_a_new_experiment_type.
