relax SVN archive

Added system tests of models m1-m4 optimised against the tm0 grid.

Added a system test for the optimisation of the m0 model-free model against the tm0 parameter grid.

Added a system test for the optimisation of the tm0 model-free parameter grid.

Generated relaxation data for model-free parameters for all of the local tm models.

This can be used for testing both the 10 local tm models and the normal 10 model-free models.

Created the spectral_density_mf_ext() function for the extended model-free theory.

This calculates the spectral density values at the given model-free parameter values.

Converted the rest of the S2 variables to s2.

Changed the S2 parameter to lower case in spectral_density_mf_orig().

Chemical exchange relaxation is now handled properly in the relaxation_data() function.

The back-calculated relaxation data is now correct for model-free models with Rex.

Te values of zero can now be handled by the spectral_density_mf_orig() model-free method.

The initial parameters are now slightly perturbed in the 3 tm2 grid system tests.

This allows the optimisation to be a bit challenged.