added top down capability
added top down capability

git-svn-id: http://svn.code.sf.net/p/petavision/code/sandbox@2699 7c0444ca-5550-0410-9008-faecdbe78eb5

Former-commit-id: f997dbeb0ff52e0fa38741dc42484301daae25d8
dpaiton/OpenPV,PetaVision/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,PetaVision/OpenPV,PetaVision/OpenPV,PetaVision/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,PetaVision/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV