Building the Python bindings

To enable the Python bindings petsc4py must be installed (e.g., by passing --with-petsc4py when configuring PETSc), and pybind11 must be available. Simply pass -DPARMGMC_ENABLE_PYTHON_BINDINGS=On during CMake config and then run make pymgmc. This generates a shared library object in build/python.

It is not possible yet to install this library somewhere, it can only be used from the folder build/python.