relax SVN archive

Massive expansion of the model-free chapter of the user manual including script and GUI tutorials.

The model-free chapter now has step-by-step tutorials for both the prompt/script mode and GUI mode
for the new automated model-free protocol (the d'Auvergne protocol). This includes a large set of
screenshots for the GUI mode.

Fixed the dipole_pair.define user function calls in the dauvergne_protocol.py sample script.

This is a recently introduced problem only present in the trunk.

The GUI model-free auto-analysis dipole_pair.define field values have been changed again.

These now default to @N and @H, as @N* and @H* will connect @N spins to @HE1 spins and @H spins to
@NE1 spins!

Fix for bug #20189 (https://gna.org/bugs/?20189).

The Sequence GUI element can no handle values of None.

Created the User_functions.test_value_set GUI test demonstrating the failure of the value.set user function.

Added a subsubsection label to the data model chapter of the user manual.

Spacing fix.

Removed the \pycodestar{} references in the development chapter.

This command has been deleted as \newcommand cannot have \verb inside it! The \pycodestar{x}
references have been changed to \verb*!x!.

Removed \verb from the \newcommand definitions as that is forbidden in LaTeX.

Now Python code is formatted using a small TT font.

Added a section label to the intro chapter of the user manual.