Package Open3D

[srounce]

Package Open3D in Nix. Missing from Nixpkgs, required as a dependency of Bayes3D.

Large parts of this Python module are C++ and so will likely present some challenges (several unsuccessful attempts have been made at this in the past) due to assumptions made about the build environment in the CMake configuration. Ideally this would be packaged from source however is likely to be a large task due to the complexity of Open3D's CMake configuration and how it expects to be able to mange dependencies. If it proves proves too complicated to package from source prebuilt wheels can be found on Pypi and patched during the Nix build.