relax SVN archive

Created a second test model for the free rotor frame order model.

In this case, the C-domain does not rotate about the pivot-CoM axis, but an axis tilted 30 degrees
from the pivot-CoM axis.

Fix for the structure.displacement user function.

The kabsch() function now returns the pivot of the rotation as well.

Added the translate method to the structural API.

Synchronised the atom_loop() method args in the structural API.

Updated the generic_fns.structure package __all__ list to include the superimposition module.

Fix for the structure.translate user function front end.

The back end already exists, so this is now functional.

Small fix for the new Structure.test_superimpose_fit_to_mean2 system test.

Created the structure.translate user function front end.

Created a second system test for the structure.superimpose user function using 'fit to mean'.

This translates one model, superimposes it to the original, and checks to see if the structures
shift correctly.

Implemented the 'fit to mean' algorithm for the structure.superimpose user function.