`DensfJob` missing spin part in the cube_file path

[YHordijk]

Currently when generating cube files of unrestricted orbitals the spin part is not added to the cubefile path.
E.g. a cubefile path is given as root/medium%SFO_A%78.cub instead of root/medium%SFO_A_A%78.cub.
The spin part is only given for unrestricted orbitals, so we should check first if the spin is AB or A or B.