relax SVN archive

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.

Modified the http://nmr-relax.com download page to point to relax version 1.3.13.

The Mac OS X stand-alone application is now included.

Added the relax 1.3.13 version of the user manual to the repository.

Merged r14998 from the main 1.3 line as this is essential for the user manual compilation.

The command used was:
svn merge -r14997:14998 svn+ssh://bugman@.../svn/relax/1.3

Bug fix for the compilation of the user manual.

The molecule user function class used the temporary variable i, which was causing the
fetch_docstrings script to fail.

Changed the version in the version file to 1.3.13.

Merged the CHANGES file for relax version 1.3.13 back into the main 1.3 line.

The command used was:
svn merge -r14994:14995 svn+ssh://bugman@.../svn/relax/tags/1.3.13