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This merge prepares the nn_interface, cnn and resnet modules for release 2.0

Modifications include:

nn_interface

1. Add option to save training logs as .csv and/or tensorflow log files
2. Automatically generate text for displaying progress on screen/saving from the selected metrics.
3. Expand the allowed metrics and loss functions in the interface
4. Add tests
5. Add documentation

cnn

1. Implement cnn architecture
2. Wrap cnn architecture with the standard interface
3. Add Tests
4. Add documentation

resnet

1. Implement cnn architecture
2. Wrap cnn architecture with the standard interface
3. Add Tests
4. Add documentation

Obs.: Most of the docstrings have been written, but I want to add at least one example that illustrates the most common way to instantiate the CNNInterface and ResNetInterface classes.