relax SVN archive

Bug fix for the scale arg unit test of the structure.create_diff_tensor_pdb() user function.

Bin args are now caught as well.

Bug fix for the model arg unit test of the structure.read_pdb() user function.

Bin args are now caught as well.

Bug fix for the structure.read_pdb() user function.

The incorrect RelaxError was being raised for the model argument.

Bug fix for the model arg unit test of the structure.read_pdb() user function.

The value is a str, not an int.

Wrote 16 unit tests for all args of all structure user functions.

Modified the structure.vectors() user function to use the spin_id string.

It was previously using the residue number and name id system.

Converted all the 'structure' user functions to the new relax design.

Bug fix for the value arg unit test of the value.set() user function.

The valid str arg types are now being caught and skipped.

Updated the value arg unit test of the value.set() user function to use another new RelaxError.

Added a missing RelaxError import.