[WIP] Cython based building and linking of C++ simulator

[chriseclectic]

Example of building and linking the C++ simulator using cython. Based on PR #386

Description

Adds an cython-build-example folder into the qasm-simulator-cpp folder which contains an example_setup.py script for building and wrapping the simulator using cython, and an example_simulation.py for running the simulator.

This can be run using

cd src/qasm_simulator_cpp/cython-build-example
python example_setup.py build_ext --inplace
python example_simulation.py

Motivation and Context

This allows cross platform building of the simulator by linking to the BLAS libraries already used by Numpy (such as MLK if python is installed with Anaconda).
It allows calling as a native python class without needing to use subprocess, and forwards C++ exceptions to python exceptions.

How Has This Been Tested?

• It has been tested with a simple example script
• The build has been tested on MacOS 10.13 building with xcode developer tools, homebrew gcc-7, and linking against anaconda MKL or apple accelerate framework, on Windows 10 using MSVC 2015 and anaconda MKL, on Ubuntu 16.04 using GCC 5 and anaconda MKL.

[nonhermitian]

Not sure why the tests cannot find the qasm_simulator_cpp file. Builds and tests pass locally for me.

[nonhermitian]

At least with regards to the Cython wrapping, Chris and I tested it in every standard configuration possible, and it works.

The next step would be to either move to setuptools, or take the source generated by Cython and do the build via the make file.

[chriseclectic]

Rebased after merge of #386

[diego-plan9]

Closing after the discussion at the meeting, as it seems superseded by #412.