fix sheBangs for python3

A lot a smalls things on msys2/mingw64 config :

• Fix shebang to python3
• port to mingw64 (msys2) : minor changes
• remove the old (unusable anymore luc.cmake)

CMake/msys2-mingw64.cmake

-# Copyright 2020 University of Liège
-# 
-# Licensed under the Apache License, Version 2.0 (the "License");
-# you may not use this file except in compliance with the License.
-# You may obtain a copy of the License at
-# 
-#     http://www.apache.org/licenses/LICENSE-2.0
-# 
-# Unless required by applicable law or agreed to in writing, software
-# distributed under the License is distributed on an "AS IS" BASIS,
-# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-# See the License for the specific language governing permissions and
-# limitations under the License.
-
-# MSYS2 Makefiles (pour MinGW64)
-# MinGW Makefiles (pour "mingw64 - -make")
-#
-#  PATH=c:\MinGW\bin;C:\MinGW\msys\1.0\bin (en desactivant "sh.exe" du PATH)
-# ou
-#  PATH=c:\MinGW\bin
-
-#STRING(REGEX REPLACE "\\\\" "/" MYLOCAL $ENV{MYLOCAL})
-
-SET(CMAKE_GENERATOR "MSYS Makefiles" CACHE INTERNAL "" FORCE)
-
-FIND_PROGRAM(CMAKE_CXX_COMPILER NAMES g++)
-FIND_PROGRAM(CMAKE_C_COMPILER   NAMES gcc)
-FIND_PROGRAM(CMAKE_MAKE_PROGRAM   NAMES mingw32-make)
-
-SET(WAVES_USE_MUMPS       ON CACHE BOOL "" FORCE)
-
-SET(WAVES_USE_MKL    OFF CACHE BOOL "" FORCE)
-SET(BLA_VENDOR    "OpenBlas" CACHE STRING "" FORCE)
-
-SET(WAVES_USE_TLNOS    OFF CACHE BOOL "" FORCE)
-#SET(WAVES_USE_TBOXVTK    OFF CACHE BOOL "" FORCE)