complete DotProductSimilarityLayer and its test file. make them
compiled without error, not test yet
	modified:   include/caffe/vision_layers.hpp
	modified:   src/caffe/layers/dot_product_similarity_layer.cpp
	modified:   src/caffe/layers/dot_product_similarity_layer.cu
	new file:   src/caffe/test/test_dot_product_similarity_layer.cpp