relax SVN archive

Redirected the download links for relax 2.1.1, 2.1.2, and 2.2.1.

These links at http://www.nmr-relax.com/download.html now point to
http://www.nmr-relax.com/download_request.html.

Backported the relax 2.2.5 changes file additions to trunk.

The command used was:
svn merge -r19097:19098 svn+ssh://bugman@.../svn/relax/tags/2.2.5 .

Updated the changes file for relax 2.2.5.

Updated the lib package __all__ list.

Some more unit test fixes.

Another attempt at fixing the unit tests of the pec module.

Clean up of the pipe_control package __all__ list.

Shifted the unit tests of the pec module to the correct location.

Converted the OpenDX package pipe_control.opendx into a module.

As most code was shifted to lib.opendx, the code was small enough to merge into one module.

Deleted an OpenDX function which has been merged into lib.opendx.files.