relax SVN archive

Created system tests for the rest of the numerical dispersion models.

These include Relax_disp.test_hansen_cpmg_data_ns_2site_expanded,
Relax_disp.test_hansen_cpmg_data_ns_2site_star and
Relax_disp.test_hansen_cpmg_data_ns_2site_star_full.

This checks the 'NS 2-site expanded', 'NS 2-site star', and 'NS 2-site star full' numerical
dispersion models against some truncated CPMG data from Flemming Hansen. The parameter checks have
not been updated for the 'NS 2-site expanded' and 'NS 2-site star full' models as there appears to
be bugs.

Created the Relax_disp.test_hansen_cpmg_data_ns_2site_3D_full system test.

This checks the 'NS 2-site 3D full' numerical dispersion model against some truncated CPMG data from
Flemming Hansen. The parameter checks have not been updated as there appears to be a bug.

Created the Relax_disp.test_hansen_cpmg_data_ns_2site_3D system test.

This checks the 'NS 2-site 3D' numerical dispersion model against some truncated CPMG data from
Flemming Hansen.

Fixes for all of the definitions of the k_AB and k_BA exchange parameters.

These were inverted in all parts of relax. The changes only affect the numerical dispersion models.

Updated the parameter checks in the Relax_disp.test_hansen_cpmg_data_CR72_full system test.

Expanded the dispersion target function class docstring to include all current dispersion models.

Created the Relax_disp.test_hansen_cpmg_data_CR72_full system test for checking the 'CR72 full' model.

Simplified the test_hansen_cpmg_data_*() system tests by shifting most shared code into setup_hansen_cpmg_data().

Fix for the lib.dispersion.ns_2site_expanded module for the missing sqrt() function import.

Import fix for the 'NS 2-site expanded' dispersion model target function.