relax SVN archive

The molecule wizard now has the molecule artwork.

The path for the wizard artwork is now in the paths module.

The user function window GUI base class now has a box sizer and the wizard image placed inside it.

Created an image for the molecule wizards.

The molecule.add user function GUI element is now partly functional, in that a blank window is shown.

The empty window is now being created, and all the user function windows are now cleanly destroyed
on exit.

Created the infrastructure for the molecule user function GUI elements.

Initialised the molecule user function GUI element class.

Created the UF_window base class for all user functions requiring generic windows.

Renamed build_menu_sub_item() to _build_menu_item().

Sub-menus are now supported in the main relax menu bar.

The 'User functions->molecule->add' sub-menu item has been added, but is not yet functional.