Revert "Adjusted loss function to treat each element in a batch individually"
Revert "Adjusted loss function to treat each element in a batch individually"

This reverts commit 7ee1ade78284ecb5c4454e43870c262be30e04d9.

NifTK/NiftyNet,NifTK/NiftyNet,NifTK/NiftyNet,NifTK/NiftyNet