relax SVN archive

Improvement for the relaxation data back-calculated for the diffusion tensors.

The back-calculated relaxation data now taked the truncation of the atom positions in the PDB into
account.

Bug fixes for the ri back-calculation and diff tensor optimisation system test scripts.

The angles units of radians needs to be specified!

The PDB vectors are no longer rotated.

However the vectors are now rotated into the diffusion frame for the calculation of the relaxation data.

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.