fix bug introduced by warning logs: errors didn't print because they
are logged to the warnings file
Merge pull request #661 from jeffdonahue/fix-error-output

Fix bug introduced by warning logs (errors didn't print)
use layer_param instead of layers_[layer_id]->layer_param()
Add param_propagate_down_ vector to layer, populate according to
blobs_lr in Net::Init
Make ConvolutionLayer and InnerProductLayer abide by param_propagate_down_
Use Blobs instead of SyncedMemorys for the bias_multiplier_'s.