Create a prepackaged model server for PyTorch Models

[axsaucedo]

PyTorch is quite a popular library, adding a prepackaged model server would allow for deploying custom PyTorch models, but would also allow for some of the popular models that are trained using PyTorch.

For background information, it was attempted to build a model for PyTorch Hub models in #642, but given that some models are too big, it could not be done (and the init containers could not be used either).

[seldondev]

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[ukclivecox]

TorchServe is now available: https://github.com/pytorch/serve