rename lenet dir to mnist
add mnist autoencoder example necessities (sigmoid cross entropy loss
layer, sparse gaussian filler)
enable DataLayer to output unlabeled data
mnist autoencoder test proto bugfix: add sigmoid layer before loss
make solver able to compute and display test loss
change lenet dir to 'mnist' in docs
mnist_autoencoder_solver cleanup
add sigmoid cross ent layer unit tests
clear sigmoid top vec at initialization
change to correct next layer id for merge
Merge pull request #330 from jeffdonahue/mnist-autoencoder-example

MNIST autoencoder example