relax SVN archive

Bug fix for the ResidueContainer.add_item() method.

The select flag is now set when replacing element 0.

Bug fix for the SpinContainer.add_item() method, the select flag is now set when replacing element 0.

Code shift, similar to that of r5443.

Shifted the spin number check (cannot have 2 spin with the same number) and 1st element replacement
(if that SpinContainer is empty) code from generic_fns.spin.create() to the relax data storage
object SpinContainer.add_item() method.

Code shift, similar to r5443.

Shifted the 1st element replacement code (if the MolecularContainer is empty) from
generic_fns.molecule.create() to the relax data storage object MoleculeContainer.add_item() method.

Code shift.

Shifted the residue number check (cannot have 2 residues with the same number) and 1st element
replacement (if that ResidueContainer is empty) code from generic_fns.residue.create() to the relax
data storage object (the ResidueContainer.add_item() method).

Added an ID string to load_spins() to fix a bug in the return_residue() and return_spin() calls.

Bug fix for the test_pdb() system test.

Expanded the data structure testing in the system test for loading of a sequence from a PDB file.

Buf fix for the system test for the loading of a sequence from a PDB file.

Only 12 residues exist in the PDB file.

Bug fix in the load_spins() function.

Renamed incorrectly named variables.