relax SVN archive

Backported the relax 3.3.7 CHANGES file changes to trunk.

The command used was:
svn merge -r27810:r27811 svn+ssh://bugman@.../svn/relax/tags/3.3.7 .

Updated the http://www.nmr-relax.com/download.html webpage for the relax 3.3.7 release.

Updated the relax API documentation at http://www.nmr-relax.com/api/3.3/ to version 3.3.7.

Updated the relax HTML manual at http://www.nmr-relax.com/manual/index.html to version 3.3.6.

Changed the download links for relax 3.2.2 and 3.3.0 to 3.3.5.

These now point to http://www.nmr-relax.com/download_request.html, as the distribution files have
been removed from the server.

Updated the CHANGES document for relax 3.3.7.

Added the relax 3.3.7 PDF manual to the repository.

Updated the version number to relax 3.3.7.

relax version 3.3.7.

This is a major feature and bugfix release. New features include the statistics.aic and
statistics.model user functions, plotting API advancements, huge speed ups for the assembly of
atomic coordinates from a large number of structures, the sorting of sequence data in the internal
structural object for better structural consistency, conversion of the structure.mean user function
to the new pipe/model/molecule/atom_id design, and improvements to the rdc.copy and pcs.copy user
functions. Bugs fixed include the incorrect pre-scanning of old scripts identifying the
minimise.calculate user function as the old minimise user function, Python 3 fixes, and the failure
in reading CSV files in the sequence.read user function.

Epydoc documentation fix for the lib.structure.pdb_write_handle_atom_name() function.