relax SVN archive

The wizards for the individual user function pages are now recycled.

This should speed up the GUI (and the GUI tests massively). Closing the wizard calls the Close()
rather than Destroy() method, so the wizards are still in memory. A new call to an old GUI uf
object will simply call SetValue() for all keyword arg GUI elements, hence reset the element.

The Wizard GUI object has been modified to only add the buttons if they do not currently exist.
Without this, a new set of buttons is added each time the user function wizard appears.

The GUI base class now has access to math.pi.

This is necessary as the system test scripts are run in this namespace rather than the interpreter
namespace which has pi defined.

The Combo_list GUI input element can now handle values typed out by the user.

This affects both the GetValue() and SetValue() methods.

The value.set user function 'param' arg can now be manually set by the user rather than selected.

A number of N-state model parameters require this.

Better handling of empty data in the Sequence.GetValue() method.

The non-supplied user function args in the GUI tests are now set to the default.

This is for the _execute_uf() base method, and is essential for the free file format where the
column args must, in many cases, be set to None.

Fix for the free file format error column.

In a number of places it was being referred to as 'err_col' rather than 'error_col'. This is due to
legacy GUI code.

Updates to the N-state model specific code.

The default_value() and return_data_desc() methods are now defined, and the data_names() method
returns a few parameter names.

Fix for the gui.string_conv.gui_to_py() function - Syntax or other errors are now handled.

This is an issue for the value.set user functions where the text '15N' causes a SyntaxError to be
raised by the eval() call.

Fixed the N-state model description so that it is no longer about domain motions.

This stands out in the GUI when creating data pipes!