mdfitter update


git-svn-id: svn+ssh://svn.cern.ch/reps/lhcb/Urania/trunk/PhysFit/B2DXFitters@168806 4525493e-7705-40b1-a816-d608a930855b
correlations update


git-svn-id: svn+ssh://svn.cern.ch/reps/lhcb/Urania/trunk/PhysFit/B2DXFitters@168853 4525493e-7705-40b1-a816-d608a930855b