relax SVN archive

Python 3 fix for one of the old scripts in the test suite directories.

Removed a debugging printout.

Missing import for the relaxation dispersion auto-analysis (from r22796).

Fix for bug #21924 (https://gna.org/bugs/?21924).

This is the failure to output 2D Grace plots for the R20, R20A, R20B, and R1rho0 relaxation
dispersion parameters. A simple test for missing data fixed the problem.

The relaxation dispersion auto-analysis now outputs the R20, R20A, R20B, and R1rho0 parameters.

This includes both text files and 2D Grace plots.

Updated the text for the software verification tests in the test suite.

Shifted the relax library independence developer script into the software verification tests.

The functionality of the devel_scripts/test_library_independence.py script is now within the
Library.test_library_independence software verification test. Therefore the script has been
deleted.

Created a new test category for the relax test suite - the software verification tests.

This is part of the full test suite or can be run by itself using the new --verification-tests
command line option. Such tests are best described by
https://en.wikipedia.org/wiki/Verification_and_validation_%28software%29. These tests will be used
to make sure that the design aims of the relax source code are satisfied. For example that the
relax library is independent from the rest of relax. Or that the package __all__ lists actually
contain all modules and sub-packages (these tests are currently part of the unit tests).

Editing of the relax command line option descriptions.

Removed the automatic axis labelling in the lib.software.grace.write_xy_header() function.

This is the automatic labelling based on the parameter Grace strings and units of the specific
analysis type. This is now preformed by the specific analyses themselves so the automatic code is
not needed or used.

This allows the dependence on the pipe_control.pipes module and the specific analysis API to be
removed making the relax library now 100% independent from the rest of relax.