relax SVN archive

Changed the test suite reference value for eta so the test passes after the equation modification.

This change follows the one for r6665 (http://svn.gna.org/viewcvs/relax?rev=6665&view=rev) and had
already been made on the 1.2 line, but was also needed on the 1.3 line. See r6611
(http://svn.gna.org/viewcvs/relax?rev=6611&view=rev) for details.

Bug fix for the load_spins() function.

Molecule, residue, and spin information can be missing and the function still work.

Some changes towards the new design.

The script doesn't work yet and will be introduced into the test suite for further debugging.

The internal PDB object atom_loop() method now can return the average atom properties, if asked.

The internal PDB object atom_loop() method now recognises the ave arg, but does nothing when True.

Added the str_id arg to the Scientific PDB object atom_loop() method.

Added the ave arg to all atom_loop() methods to allow just the average properties to be returned.

Docstring modification for the atom_loop() internal PDB object method.

Added the str_id arg to the atom_loop() structural API method.

Added the ability to select the structure to load the spins from in the load_spins() main method.