Converted the Relax_disp.test_sprangers_cpmg_data_auto_analysis system test to not use the auto-analysis.

The test has been renamed to Relax_disp.test_sprangers_data_to_mq_ns_cpmg_2site.  The optimisation
is now for the cluster and has been severely cut back.  The 'MQ NS CPMG 2-site' model appears to be
rubbish anyway - it looks to be indeterminate with multiple solutions, and possibly infinite lines
of solutions.  The test now passes, and quickly.
Created the Relax_disp.test_sprangers_data_to_mq_cr72 system test.

This was copied from the Relax_disp.test_sprangers_data_to_mq_ns_cpmg_2site system test and the
model changed to 'MQ CR72'.

This follows the tutorial for adding relaxation dispersion models at:
http://wiki.nmr-relax.com/Tutorial_for_adding_relaxation_dispersion_models_to_relax#The_test_suite
Added the 'MQ CR72' model to the dispersion variables.

This is the Carver and Richards (1972) 2-site model expanded for MQ CPMG data by Korzhnev et al.,
2004.

This follows the tutorial for adding relaxation dispersion models at:
http://wiki.nmr-relax.com/Tutorial_for_adding_relaxation_dispersion_models_to_relax#Adding_the_model_to_the_list
Added the 'MQ CR72' model to the relax_disp.select_model user function frontend.

This is the Carver and Richards (1972) 2-site model expanded for MQ CPMG data by Korzhnev et al.,
2004.

This follows the tutorial for adding relaxation dispersion models at:
http://wiki.nmr-relax.com/Tutorial_for_adding_relaxation_dispersion_models_to_relax#The_relax_disp.select_model_user_function_front_end