Translations:Import/Export IFC - compiling IfcOpenShell/2/en

Introduction
It was a such a hard investigation on how to get a working copy of IfcOpenShell-python on OSX/macOS in order to import/export IFC files that I'm sharing this tutorial in case it helps more people. My system is OSX 10.11.6, 64bits with Python 2.7.11, it might work for you if you have also OSX as they are often 64bits but may differ from mine. The procedure might be very similar if you run Linux or Windows but it probably have some differences.