relax SVN archive

Updated the http://www.nmr-relax.com/download.html webpage for relax version 3.1.0.

Changed the version number to 3.1.0.

Backported the relax 3.1.0 CHANGES file addition to trunk.

The command used was:
svn merge -r21689:21690 svn+ssh://bugman@.../svn/relax/tags/3.1.0 .

Updated the CHANGES file for relax 3.1.0.

Added the relax 3.1.0 user manual to the repository.

relax version 3.1.0.

This is a major feature release which adds full support for the analysis of relaxation dispersion
data.

Bug fix for the previous commit (r21686).

Improvements in the test_suite.clean_up.deletion() function.

It is now more fail safe on Python 3 by completely avoiding the WindowsError checking.

The relax system test base tearDown() method should now be fail proof.

Most code is now warped in a 'try: except: pass' block to catch all failures.

Fix for the specific_analyses.relax_disp.optimisation.back_calc_r2eff() function.

The R2eff error data structure when the cpmg_frqs or spin_lock_nu1 argument is supplied was all
zeros, whereas it should all be ones. This was causing many divide by zero numpy warnings to appear
on certain operating systems (Mac OS X).