Shell model code NUSHELL tips

1. In old version of NUSHELL, be careful for the 'psd' model space.
   The single particle levels defined in the 'psd.sp' and interactions like 'psdmk.int'
   may be not consistent.
   The level ordering in original 'psd.sp' file is

   1 1 1 3  (p3/2)
   2 1 1 1  (p1/2)

   But, it have to be changed as follows to be consistent with the definitions in 'psdmk.int' interaction file.

   1 1 1 1  (p1/2)
   2 1 1 3  (p3/2)

---UNDER CONSTRUCTION