relax SVN archive

Fix for the numbering of the TER record and subsequence HETATM records in the PDB file creation.

The structure.write_pdb user function now creates the correct TER record after the ATOM records,
and the HETATM records are renumbered if needed.

Added the validate_models() method to the structural API.

This is used to check that the models are 100% consistent.

Added the centroid argument to the structure.superimpose user function.

This allows for the superimposition of structures assuming a pivoted motion.

Another fix for the print out of the structure.superimpose user function.

The final step of calculating the displacements to the final mean structure was incorrectly output.
This has no effect on the algorithm.

Fix for the structure.superimpose user function print outs - the angle is now in degrees.

Removed the 1.2 manuals from the http://www.nmr-relax.com/docs.html documentation page.

Updated the http://nmr-relax.com API manual to version 1.3.13.

Updated the index file at http://www.nmr-relax.com/api/ for the new 1.3.13 version.

Updated the http://nmr-relax.com HTML user manual to version 1.3.13.

Modified the release checklist for large files!

The Mac OS X DMG file is ~120 Mb, so the uploading command for the distribution files has been
updated to show the progress.