Adding NN and CNN class implementations using Shadow

[stompsjo]

This introduces two classes (ShadowNN and ShadowCNN) that can be used for semi-supervised machine learning with neural networks, Shadow, and PyTorch. This includes typical scikit-learn-esque methods like train and predict as well as methods for hyperparameter optimization and saving the model to file.

[coveralls]

Pull Request Test Coverage Report for Build 3363795138

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

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Totals
Change from base Build 3348444582:	0.0%
Covered Lines:	221
Relevant Lines:	221

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💛 - Coveralls

[stompsjo]

Closing this PR in favor of #50