Update master branch with various LHCb decay model additions/fixes over the past 6 months.

Corrected EvtSLDiBaryonAmp bugs/issues in the BToDiBaryonlnupQCD model:
parity, amplitude terms and B momentum reference frame variables.

Corrected treament of spinor indices in EvtRareLb2Lll.

Updated the EvtBcVHad model to also handle Bc -> psi Ks K decays.

Add new decay model EvtBsMuMuKK (BS_MUMUKK) for Bs to J/psi (mu+mu-) K+K-.