usage edit:
	modified:   examples/imagenet/create_imagenet.sh
set gpu device no:
	modified:   examples/imagenet/imagenet_solver.prototxt
	modified:   examples/mnist/lenet_solver.prototxt

fix the bug of invalid configuration argument, restrict max num of
blocks
	modified:   include/caffe/common.hpp
	modified:   src/caffe/common.cpp

edit max file numbers which leveldb can open, solve the bug of heavy
load of memory:
	modified:   src/caffe/layers/data_layer.cpp
	modified:   src/caffe/layers/relu_layer.cu