Msys build

Context

This merge request brings a new build on Windows using MSYS2.

Major changes

• MSYS2 build is now supported for Windows platforms

Minor changes

• Apache 2.0 license has been added to each file (more or less)
• [Flow] Transpiration boundary condition and dummy coupler have been added to prepare Amaury's work on viscous/inviscid coupling

Tests

• Passed on ubuntu 18.04, debian (gaston)

README.md

 # waves
 Waves is a collection of general utilities and finite element tools for solving various PDE. The code is written in C++ interfaced in python through SWIG, and is developed at the University of Liège.
 
-[![Apache License Version 2.0](https://img.shields.io/badge/license-Apache_2.0-green.svg)](LICENSE)
-
-[![Run Status](https://gitlab.uliege.be/am-dept/waves/badges/master/pipeline.svg)](https://gitlab.uliege.be/am-dept/waves/pipelines)
-
 ![](/dox/img.png)
 
 ## Features