relax SVN archive

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.

Fix for the new _create_sub_menu() method.

Shifted out the generic sub-menu building code from _user_functions() to _create_sub_menu().

Shifted the 'user function' sub-menu construction into _user_functions().

Shifted out the GUI main menu bar into its own module.

Improvements to the unfolded molecule icon - there is now residual structure!

The molecule icon changes from folded to unfolded as the tree is opened and closed.

Added the unfolded molecule icon to the paths module.

Added an basic icon for an unfolded molecule.

The 'Spin tree view' menu entry has been renamed to 'Spin view', and the spin icon is now used.