relax SVN archive

The Value GUI input element UpdateChoices() method now restores the current selection.

This matches the Combo_list GUI element changes.

Renamed all of the ResetChoices() GUI methods to UpdateChoices().

This is because they are for updating a list while retaining the current selection.

The Combo_list GUI input element ResetChoices() method now remembers the current selection.

This allows the selection to be restored when the element is updated, rather than resetting to the
default value.

Fix for the Sequence GUI input element GetValue() method for list types.

The GUI test _execute_uf() base method now handles non-keyword args, by converting them to keyword args.

All system test scripts are now executed through the base script_exec() method.

This allows them to be run in the GUI tests as well.

Fix for the file selection and directory handling in the GUI base test _execute_uf() method.

This now handles the situation of when no directory argument is supplied.

The execute_uf() method is now private!

Final fix for the rdc_tensor.py N-state model system test script.

Added all of the N-state model system tests as GUI tests.