relax SVN archive

Allowed the align_tensor.display() arg to be None (to display all tensors).

Set the 2-domain N-state model gradient and Hessian methods to None.

Fixes for the test___disassemble_param_vector() unit test.

Added a test to __disassemble_param_vector() to set if the model has been selected.

Fixed the test___assemble_param_vector() unit test.

Added a test to see if the model has been selected.

Fixes for all the N-state model unit tests.

Changed the PCS scaling factor.

Fix for the paramagnetic centre to nucleus distances.

The distances are now converted from Angstrom to meters.

Shrunk the size of the default PCS errors, so the chi-squared value is comparable to the RDC.