relax SVN archive

Typo fix for the new lib.curve_fit.exponential.exponential_2param_neg() function.

Created the new lib.curve_fit.exponential module for exponential curve-fitting.

This contains the single exponential_2param_neg() function which will be used for the relaxation
dispersion target functions. This is based on Sebastien Morin's function exp_2param_neg in
maths_fns.exponential.c in his dormant inversion-recovery branch.

Created the lib.curve_fit package and associated unit tests.

This will be used for holding modules such as for exponential curve-fitting required for the
relaxation dispersion analysis.

Missing import in the target_functions.relax_disp module.

The scaling flag is now initialised in the relaxation dispersion target function class.

The relax_disp function _grid_search_setup() now operates in the same way as the relax_fit code.

This function originates from the 'relax_fit' specific analysis code, but that code has since
evolved. The 'relax_disp' code now mimics the new code, returning lists of grid search increments
and upper and lower limits.

The specific_analyses.relax_disp module is now using minfx correctly.

The minfx grid search is no longer part of generic_minimise() and must be called separately.

Created the Relax_disp.test_exp_fit system test for checking the relaxation dispersion 'exp_fit' model.

The lib.software.sparky.read_list_intensity() function can now handle lowercase in the residue names.

Added some synthetic data to test the 'exp_fit' relaxation dispersion model fitting.

These are just basic synthetic exponential curves. R2eff and I0 should be very easy to find.