wfn file manipulations

For some specific appliacations the wfn file must be modified because GAUSSIAN contains a bug in the case of ROHF calculations (all the orbitals are doubly occupied!). There are two wfn manipulations:

1. ROHF: change occupation number of singly occupied orbitals

    
   MO  5  MO 0.0  OCC NO = 2.0000000  ORB. ENERGY =   0.0
   
   MO  5  MO 0.0  OCC NO = 1.0000000  ORB. ENERGY =   0.0
   

2. ROHF and CASSCF: specify orbital contribution to $M_S$ (in fact twice). The 0.0 after MO should be changed to -1 ($\beta$), 0 (mixing true singlet), 1 ($\alpha$), example

   MO  5  MO 1.0  OCC NO = 1.0000000  ORB. ENERGY =   0.0