Return CNNTrain2Caffe2 in Backend in case of CAFFE2
Return CNNTrain2Caffe2 as well in Backend in case of CAFFE2. Difference between both backend MXNET and CAFFE2 can be seen reviewing the generated file CNNCreator once this branch is merged as well as the branch "layer-templates-caffe2" in the project CNNArch2Caffe2.