relax SVN archive

Python 3 bugfix for the Relax_disp.test_bug_24601_r2eff_missing_data system test.

Tab characters rather than spaces made the system test script unloadable in Python 3.

Clarifications and minor expansion of the release checklist document.

Bug fix for the pcs.structural_error user function.

The user function now uses a real multivariate normal distribution for sampling atomic positions.
The previous random unit vector + univariate Gaussian sampling does not correctly reproduce the
multivariate normal distribution.

Updated the relax version number to 4.0.3 on the http://www.nmr-relax.com/api/index.html webpage.

Updated the relax API documentation at http://www.nmr-relax.com/api/4.0/ to version 4.0.3.

Updated the relax HTML manual at http://www.nmr-relax.com/manual/index.html to version 4.0.3.

Updated the http://www.nmr-relax.com/download.html webpage for the relax 4.0.3 release.

Backported the relax 4.0.3 CHANGES file changes to trunk.

The command used was:
svn merge -r28265:28266 svn+ssh://bugman@.../svn/relax/tags/4.0.3 .

Updated the CHANGES file for relax 4.0.3.

Added the relax 4.0.3 manual to the repository.