relax SVN archive

Removed a duplicated comment.

Modified the N-state model metal_pos_opt.py system test script.

This is to test optimisation with the new paramagnetic position gradients.

Fix for the assembly of the N-state model linear constraints.

These were not set up correctly when the populations and paramagnetic position are optimised
together.

Constraints are now allowed for the paramagnetic position optimisation in the N-state model.

This is because the gradients are implemented and functional.

Bug fix for the calculation of the PCS gradient with respect to the paramagnetic coordinates.

This is in the ave_pcs_tensor_ddeltaij_dc() function - the gradient needs to be converted back to
the Angstrom units of the paramagnetic position parameters.

Comment fixes in the ave_pcs_tensor_ddeltaij_dc() and pcs_constant_grad() functions.

Bug fix for the N-state model optimisation of populations and paramagnetic position.

The gradient from dfunc_standard() is now correctly calculated when both are optimised.

Bug fix for the N-state model target functions - now copies of the gradient and Hessian are returned.

Expanded the N-state model target function func_standard() docstring to include the xi derivative.

This is the partial derivative with respect to the paramagnetic centre position.

The probabilities and paramagnetic position can now be simultaneously in the N-state model.

Such a combination would have previously failed to unpack the parameters correctly.