Modified the 'generic_fns.residue.copy()' function to work with the modified 'return_molecule()' fn.
Five unit test were failing due to the previous commit. This was because of a problem in 'generic_fns.residue.copy()' that wasn't previously detected.
Authored by: bugman 2007-11-04
Parent: [r3420]
Child: [r3422]
