lint
fixed unnecessary conversions in test_solver, and rearraged common.hpp a bit
fix compiler complaint in matcaffe
Solver switching support & implementation of Nesterov's accelerated gradient and AdaGrad
restored vituals in solver.hpp
converted pointers to shared_ptr
fixed solver constructor in train_net.cpp
improved numerical stability for AdaGrad
bugfixes for AdaGrad
Added L1 regularization support for the weights
fixed caffe.proto after a mistaken rebase
Addressed Yangqing's comments
fixes after rebase