Add input/outputShape information to all KDocs of layers

[zaleslaw]

We need to have better documentation for our layers. A few layers have inputShape/outputShape information in the KDocs, copied from Keras documentation, for example GlobalAvgPool2D

Please add the same documentation section to all the following layers:

• [ ] ELU
• [ ] LeakyReLU
• [ ] PReLU
• [ ] ReLU
• [ ] Softmax
• [ ] ThresholdedReLU
• [ ] DepthwiseConv2D
• [ ] SeparableConv2D
• [ ] Dense
• [ ] Input
• [ ] BatchNorm
• [ ] AvgPool1D
• [ ] AvgPool2D (should be in one format)
• [ ] AvgPool3D
• [ ] GlobalMaxPool1D
• [ ] GlobalMaxPool2D
• [ ] GlobalMaxPool3D
• [ ] MaxPool1D
• [ ] MaxPool2D
• [ ] MaxPool3D
• [ ] Flatten
• [ ] ZeroPadding1D
• [ ] ZeroPadding2D
• [ ] ZeroPadding3D

[dosier]

Hey, I'd like to contribute a bit again. Could do this one.

One question I have, in some cases Keras specifies different shapes depending upon the data_format being channels_first or channels_last. I do see we have this implemented for the ZeroPadding.. layers but not for any others.

From what I understand the default implementation uses the channels_last format.

There are two conventions for shapes of images tensors: the channels-last convention (used by TensorFlow) > and the channels-first convention (used by Theano).

Deep Learning with Python - François Chollet (https://stackoverflow.com/a/54967450/12089702)

So I guess for now we just omit the part about the data_format and only take the channels_last part?

[dosier]

Also I guess Input and Flatten do not need this documentation?