change specification of forward/backward function and fix layer
definitions appropriately
fix net_speed_benchmark so 'make all' works
make tests compile and pass
test_gradient_check_util: blobid -> blob_id
gradient checker optimization with forward pass loss: only need to run
backward pass to compute analytic gradient (the thing being checked) now
remove empty file added to create placeholder commit
revert unnecessary reordering of lines in softmaxwithlosslayer backward