relax SVN archive

The average_intensity() dispersion function now accepts the offset argument.

This is for better support of combined offset and spin-lock varied R1rho-type data. The argument is
then passed into the find_intensity_keys() function.

Updated the news announcement link for relax version 3.1.1 at http://www.nmr-relax.com/download.html.

The correct link is https://gna.org/forum/forum.php?forum_id=2423.

Updated the relax API documentation at http://www.nmr-relax.com/api/3.1/ to version 3.1.1.

Updated the version number to 3.1.1 on the webpage http://www.nmr-relax.com/api/.

Updated the HTML version of the relax manual to version 3.1.1.

This is for http://www.nmr-relax.com/manual/index.html.

Updated the http://www.nmr-relax.com/download.html webpage for relax version 3.1.1.

Added the relax 3.1.1 manual to the repository.

Updated the version number to relax 3.1.1.

Backported the relax 3.1.1 CHANGES file addition to trunk.

The command used was:
svn merge -r21934:21935 svn+ssh://bugman@.../svn/relax/tags/3.1.1 .

Updated the CHANGES file for relax version 3.1.1.