Display averaged loss over the last several iterations
Added Multistep, Poly and Sigmoid learning rate decay policies

Conflicts:
	include/caffe/solver.hpp
	src/caffe/proto/caffe.proto
	src/caffe/solver.cpp
Adapt lenet_multistep_solver.prototxt to current solvers
Fix init current_step
Added bvlc_googlenet prototxt and weights
Added credits for training bvlc models
Added credits and bvlc_googlenet to model_zoo.md
Warning of fallback only the first time for cudnn_pooling_layer