relax SVN archive

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.

Shifted some more OpenDX code from pipe_control.opendx.main into the new module lib.opendx.execute.