relax SVN archive

Modified the frame_order.pdb_model user function so that the three PDB files are optional.

This allows only certain components of the frame order theory to be represented in PDB format.

Fix for bug #22041, the PDB atom serial number error from the structure.write_pdb user function.

This was reported at https://gna.org/bugs/?22041.

The problem is that the structure.write_pdb user function preserves the atom numbering from the
original structure and uses that for the atom serial number. However the atom serial number must be
replaced with sequential values to produce a valid PDB file. This is fatal for any CONECT records.

Created the Structure.test_bug_22041_atom_numbering system test to catch bug #22041.

This was reported at https://gna.org/bugs/?22041.

The problem is that the structure.write_pdb user function does not create the correct atom serial
numbers.

Another fix for the dead link finding script.

And some more improvements for the dead link finding script.

More improvements for the dead link finding script.

Added another redirect to http://www.nmr-relax.com.

Some improvements for the dead link finding script.

Added some more dead links to the .setup_redirects.py script.

The script has been executed and the auto-generated files added to the repository. This should fix
most of the dead links found in the relax mailing list archives.

Created a script for finding all dead http://www.nmr-relax.com links in files of a directory tree.