relax SVN archive

The unit bond vector is now normalised - just in case - in the ri_data() function.

Fix for the tensor_setup() function.

The Dx, Dy, and Dz values were not being used (they were hardcoded).

The values from the ellipsoid optimisation is now carefully checked.

Added system tests checking the back-calculated relaxation data for all diffusion tensor types.

Fix for the generate_data.pdb() function.

The returned vectors are now rotated to the diffusion tensor frame and are rearranged to match the
PDB file residue ordering.

Modified the ri_back_calc.py to back calculate the relaxation data for the given tensor.

Copied the tensor_opt.py script to start testing the relaxation data back calculation by relax.

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.