relax SVN archive

Fixed a problem with 'self.atom_add()' where 'res_num' was being accessed as 'residue_num'.

Modified the 'self.write_pdb_file()' function to properly handle the HET records.

The function 'self.create_tensor_pdb()' has been modified for the new 'self.atomic_data' structure.

The centre of mass, vector distribution, and axes have been turned into individual residues.

Readjustment of 'self.atomic_data' and the addition of epydoc fields to 'self.atom_add()'.

The record name has been removed as this can be determined by the 'self.write_pdb_file()' function.

Expanded the 'self.atomic_data' data structure to include most of the PDB HETATM fields.

Added the function 'self.get_chemical_name()'.

This returns the chemical name corresponding to the supplied hetID string.

Rewrote the docstring of the 'self.write_pdb_file()' function to include PDB record descriptions.

Desriptions of the PDB records HET, HETNAM, FORMUL, HETATM, TER, CONECT, MASTER, and END including
tables of columns, data type, field, and definition have been added. This info comes from the
"Protein Data Bank Contents Guide: Atomic Coordinate Entry Format Description" version 2.1 (draft),
October 25, 1996.

Fixed the spelling of 'infinite' in the 1.2.8 release details.

A few small edits of the release checklist and fixed the scons target 'user_manual_html'.

Updated the manual and changed the version number to 1.2.8.