relax SVN archive

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.

A few small fixes for the generate_data.py script.

The bond length is now 1.02 Angstrom.

Removed the grid search and started optimisation of the ellipsoid diff tensor at the solution.

Fix for the internal structural object PDB writing.

The PDB format was not being followed correctly! The TER record comes after ATOM records but before
HETATM records. It is not needed if there are no ATOM records.