relax SVN archive

Created the test_load_protein_gly_N_Ca_spins_from_pdb() system test.

This tests the loading of glycine backbone amide N and Ca spins from a loaded protein PDB file.

Added the system test test_load_protein_gly_N_spins_from_pdb().

This tests the loading the glycine backbone amide N spins from a loaded protein PDB file.

Bug fix for the system test of loading the protein backbone amide N spins from a loaded PDB file.

Bug fix for the MoleculeContainer.add_item() method.

The select flag is now set when replacing element 0.

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.