Moved implementation of getLayerData() to .cpp file and started to move activity from layer to DataStore.  This means consumers of layer activity should use the getLayerData method from the data interface.
Moved implementation of getLayerData() to .cpp file and started to move activity from layer to DataStore.  This means consumers of layer activity should use the getLayerData method from the data interface.

git-svn-id: 602a26e73ae9f2a14e2bb95676f2e137fcc39919@2371 7c0444ca-5550-0410-9008-faecdbe78eb5

PetaVision/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,PetaVision/OpenPV,PetaVision/OpenPV,dpaiton/OpenPV,PetaVision/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,PetaVision/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV