relax SVN archive

The optimised spherical diffusion tensor data is now being checked.

Modified the diffusion tensor optimisation system test script for stand-alone operation.

Created the sphere and spheroid diffusion tensor optimisation system tests.

Relaxation data for the sphere and spheroid is now being generated.

test_suite.shared_data.diffusion_tensor.generate_data is now a module and used by the ellipsoid.

Copied the script to be modified for using the module in the parent directory.

Shifted the data generation script to the base directory to be used by all tensor types.

Fix for the path used in the ellipsoid diff tensor optimisation script.

Shifted the diffusion tensor optimisation system test to be specific to the ellipsoid.

The diffusion tensor system test scripts are now located in the scripts/diff_tensor directory.