Resnet50, SqueezeNet and VGG19 represented twice from different source frameworks

The model zoo currently contains three models (Resnet50, SqueezeNet and VGG19) that each have two variants which is confusing to end consumers.

Ideally these should be de-duplicated. If that doesn't make sense then they should state their differences outside of origin framework and be organized in a way that places them all in the same sub-folder/path on the repo.

Following are pointers to the existing duplicated models:

• Resnet50
  • https://github.com/onnx/models/tree/master/resnet50
  • https://s3.amazonaws.com/onnx*model*zoo/resnet/resnet50v1/resnet50v1.onnx
• SqueezeNet (different revisions of the network, likely makes sense to leave both but should consolidate their paths)
  • https://github.com/onnx/models/tree/master/squeezenet
  • https://github.com/onnx/models/tree/master/models/image_classification/squeezenet
• VGG19
  • https://github.com/onnx/models/tree/master/vgg19
  • https://s3.amazonaws.com/onnx*model*zoo/vgg/vgg16/vgg16.onnx

Review the model directories at resnet50, squeezenet, models/image_classification/squeezenet, and vgg19, along with the linked model-zoo artifacts. Determine whether the variants are duplicates or meaningful revisions, then consolidate their locations or document their differences. Done means the affected models have one clear organization and consumers are no longer confused by duplicate paths.