Draft: Add neural network prediction interface

[clevelam]

Background

• This work provides an interface to generate neural network predictions from an existing NN library. The only library currently supported in libtorch (c++ interface of the py-torch project)

Purpose of Pull Request

• Provide general draco NN interface to access generic NN backend libraries like py-torch.

Description of changes

• Provide NN wrappers providing an interface layer between draco and what ever backend NN library is chosen
• Provide py-torch NN example.
• Add py-torch to the draco dependencies configuration.

Status

• Reference:
  • Pre-Merge Code Review
  • CDash Status
• Checks
  • [ ] Travis/Appveyor CI checks pass
  • [ ] Code coverage does not decrease
  • [ ] Valgrind test passes
  • [ ] Toss3 checks pass
  • [ ] Trinitite checks pass
  • [ ] Code reviewed/approved, sufficient DbC checks, testing, documentation