relax SVN archive

Added the full_info flag arg to return_spin() to allow more info to be returned when desired.

This flag will cause the molecule name, residue number and residue name to be returned in addition
to the spin container.

Deleted the xh_vector() method from the API base class and Scientific Python PDB data object.

Shifted the XH vector calculation from the xh_vector() structural API method to the vector() fn.

This calculation can be done independently from the type of the structural data object.

The generate_spin_id() fn is now being called by the vectors() fn.

The generate_spin_id_data_array() fn is now called in the read() method.

Fixed the call to generate_spin_id() in the return_spin_from_index() function.

Renamed generate_spin_id() to generate_spin_id_data_array(), and created a new generate_spin_id().

The generate_spin_id_data_array() function generates the spin_id string from a data array whereas
generate_spin_id() generates the spin_id string from the argument values passed into it.

Added the structural API atom_loop() call to the vectors() function.

Renamed the structural API base class method num_str() to num_models().

Fixed the angles.py script used in the system tests.

The heteronuc arg to structure.vectors() has been removed.