Added support for the MQ dispersion data types to the rest of relax.
This is needed for the 'MQ NS CPMG 2-site' model, and the changes affect the dispersion data checks
and the dispersion target functions.
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.
