relax SVN archive

The scons 'install' target now creates both *.pyc and *.pyo files during installation.

The wizard page element_string_list() method can now create the special Combo_list objects.

The element_type argument is used to select between the default element and the Combo_list object.
This allows this one element to be used for all string list user function arguments, independent of
the GUI element type.

Created the wizard page ResetChoices() method for resetting the list of values in a ComboBox.

This is currently implemented for the wizard_elements.Base_value class.

Created a Clear() wizard page method for clearing a specific GUI element.

This is currently only implemented for the wizard_elements.Base_value class.

The wizard page element_string() GUI element creator read_only flag now defaults to False.

The read_only=True flag to wizard_elements.Base_value now sets a TextCtrl to the background colour.

The wizard_elements.Base_value.SetValue() method now works properly with the ComboBox.

The wizard_elements.Base_value class now can set the element to be read only.

The wizard page element_string() method now accepts all the combo box args (and a read_only arg).

Created generic_fns.pipes.PIPE_DESC_LIST which is the PIPE_DESC as a list, sorted by VALID_TYPES.

This will be used in the GUI user functions.