added cross-channel MVN, Mean-only normalization, added to layer factory, moved to common_layers

Conflicts:
	src/caffe/layer_factory.cpp
	src/caffe/layers/mvn_layer.cpp
	src/caffe/layers/mvn_layer.cu
added cross-channel MVN, Mean-only normalization, added to layer factory, moved to common_layers

Conflicts:
	include/caffe/common_layers.hpp
	src/caffe/layer_factory.cpp
minor fix for layer factory
lint