Ecole extension

[AntoinePrv]

Describe the problem or improvement suggested

For researchers to work with Ecole in C++ and Python they have two choices:

• 1. Work in a fork of Ecole, which is hard to update and will conflict with the Ecole package
• 2. Provide their own bindings

Describe the solution you would like

We want to improve on 2. by providing a template repository were all SCIP, Ecole, xtensor, pybind, CMake and setuptools have been setup.

Steps:

• [x] Add CMake GenerateExportHeader and export public symbols
• [x] Test building Ecole as shared lib in CI
• [x] Improve header names (spacing)
• [ ] Try to remove robin_hood from Graph public API
• [x] Make libecole installable
  • [x] Create CMake install instructions
  • [ ] ~Move to VCPKG for easy dependency?~
  • [x] Make components based install
• [x] Add example of how to use libecole through CMake
• [ ] Make an interface library ecole-extension #282
• [x] Test examples in CI #267
  • [x] Test libecole CMake install
  • [x] Test Python install
  • [x] Test notebooks (using papermill)
• [x] Make libecole a separate Conda package
  • [x] In dev https://github.com/conda-forge/ecole-feedstock/pull/27
  • [ ] In main
• [ ] Make an ecole-extension-helper conda package
  • [ ] With interface library?
  • [x] ~With xtensor, xtensor-python, and pybind, SCIP, and ecole dependencies~ Replaced by pinning the dependencies as run_constrained
• [x] Make sure libecole.so, headers, CMake config files... are packaged in wheel
• [x] Create extension repository https://github.com/ds4dm/ecole-extension
  • [x] use Cookie cutter ?

Describe alternatives you have considered

Additional context

• Requires #37