Use setup.py for building C++ backend

[PokhodenkoSA]

For Python users it is more convenient to work with package via setup.py file. It is the standard way to build and develop package.
So building package python setup.py install or developing package python setup.py develop should also build C++ code for backend.
Example: https://github.com/numba/llvmlite
https://github.com/numba/llvmlite/blob/1f25fa723e419e77c325a135e10acfb9b6112e8f/setup.py#L45 - from setup.py call Python script for build CMake
https://github.com/numba/llvmlite/blob/master/ffi/build.py - Python script for build CMake

User can build package via python setup.py install.
Also conda scripts become simpler.
Also developers will not require to create custom scripts for building parts of the project. All parts could be built via setup.py.

[diptorupd]

Thanks @1e-to. I tried it and it is really nice 👍