relax SVN archive

Added the missing RelaxError import statement.

Added a unit test for various types of failure of copying spin data.

Added a unit test for the failure of copying spin data to a non-existent data pipe.

Added a unit test for copying spin data between data pipes.

Added a unit test for copying spins between residues and improvements to 'test_spin.py'.

Wrote a unit test for checking the copying of spin data between molecules.

The spin user function class is now accessible from the prompt.

Copied the residue user function module to the spin module.

Removed the prompt.spin module. This will be replaced by the current residue module instead.

Removed the useless read(), sort(), and write() spin user functions.

These were remnants of the copy from the original sequence user function module.