add a look up table layer to do L2 norm loss devise
	修改：      include/caffe/vision_layers.hpp
	修改：      src/caffe/layer_factory.cpp
	修改：      src/caffe/layers/dot_product_similarity_layer.cpp
	修改：      src/caffe/layers/dot_product_similarity_layer.cu
	新文件：    src/caffe/layers/look_up_table_layer.cpp
	修改：      src/caffe/proto/caffe.proto
	修改：      src/caffe/test/test_dot_product_similarity_layer.cpp