Allow spin polarisation to be negative.
Allow spin polarisation to be negative.

Previously we only treated +ve spin polarisation (ie nalpha > nbeta) as
this is degnerate with the opposite case for RHF-type systems.  This is
not true for UHF basis sets though!

ruthfranklin/hande,hande-qmc/hande,hande-qmc/hande,hande-qmc/hande,hande-qmc/hande,hande-qmc/hande