relax SVN archive

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.

Corrected an error in the definition of eta.

This change had 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.

Updated a copyright.

Fixes for the test_load_pdb() unit test.

Bug fix for the read_pdb() method.

The structural object is only created if it does not yet exist. This bug was causing the loss of
previously loaded files.