Extract conv1D functionality from Conv1D Layer

[ocampor]

Description

As described in #528, the layer Conv1D is doing two things at a time (1) calculating a one-dimensional convolution and (2) applying the activation function. If we split this functionality into two, we enable clients to only use the conv1D. This will allow them to write code that is easier to read.

Solution

Extract the conv1D functionality into NN.swfit

[saeta]

I think this LGTM; it'd be great to have a separate unit test for the conv1D function, but I do acknowledge that the existing Conv1D layer tests do cover the function today.

Thanks for this contribution! I've kicked off CI just to confirm there are no issues.

All the best,
-Brennan

[ocampor]

Thanks @saeta, I do agree that conv1D should have it's own unit test; however, I found that all the NN functions are tested in LayerTests.swift. I analyzed the test and the functionality that is tested is the convolution and not the layer. May be it would ge a good idea to extract those tests from LayerTests.swift and create a NNTests.swift in the future?.