fixed bug in bias backprop.  unittests pass again
fixed bug in bias backprop.  unittests pass again

pimms/DeepCL,mrgloom/DeepCL,mrgloom/DeepCL,mrgloom/DeepCL,FighterLYL/DeepCL,MiniLight/DeepCL,MiniLight/DeepCL,Peilong/DeepCL,hughperkins/DeepCL,Peilong/DeepCL,MiniLight/DeepCL,Peilong/DeepCL,hughperkins/DeepCL,hughperkins/DeepCL,mrgloom/DeepCL,MiniLight/DeepCL,pimms/DeepCL,mrgloom/DeepCL,pimms/DeepCL,hughperkins/DeepCL,MiniLight/DeepCL,pimms/DeepCL,FighterLYL/DeepCL,Peilong/DeepCL,FighterLYL/DeepCL,FighterLYL/DeepCL,pimms/DeepCL,FighterLYL/DeepCL,Peilong/DeepCL,hughperkins/DeepCL