fold and unfold a block or a stack of layers

[jamesben6688]

Hello, thank you for your great work.

I wonder if you can provide a feature, where we can fold or unfold a block, for example, we may want to fold a bottleneck block, or a stack of same layers. Usually the neural network is very long, so if we can fold a block, we can have a better understanding of the whole network.

In addition, it would be better if the output size of each layer can be presented in the graph.

[lutzroeder]

@jamesben6688 can you share a sample file?

[lutzroeder]

Duplicate of #68 and #71