Adapt framework for use with the Lung Nodules study

[sam-may]

Want to use this repository to also train networks for segmentation and classification of lung nodules (also using CT scan slices as inputs).

Tentative to-do list:

• [ ] Write script for converting from Ola's hdf5 file format to the same format currently used for pneumonia segmentation studies.
• [ ] Create a generic TrainHelper class that is neither segmentation nor classification specific. Can then create SegmentationHelper, ClassificationHelper, and SegmentationPlusClassificationHelper classes which derive from TrainHelper.
• [ ] Implement 2D CNNs for classification, in the form of "regular" classification network as well as in the form of a U-Net with classification at the bottleneck.

[sam-may]

Closing this issue to redefine various lung nodule items in separate issues