Fix/update install process. Try to fix my local mess...

CMakeLists.txt

cmake/HySoPInstallSetup.cmake

cmake/PythonInstallSetup.cmake

cmake/fortran_utils.cmake

docs/config/hysop.doxyfile.in

docs/sphinx/users_guide/stretching.rst

hysop/constants.py

hysop/fields/tests/test_variable.py

hysop/fields/variable_parameter.py

hysop/methods_keys.py

hysop/mpi/topology.py

hysop/numerics/interpolation.py

hysop/numerics/odesolvers.py

hysop/numerics/remeshing.py

hysop/numerics/tests/test_finite_differences.py

hysop/numerics/tests/test_remesh.py

hysop/numerics/utils.py

hysop/operator/absorption_bc.py

hysop/operator/discrete/absorption_bc.py

hysop/operator/discrete/multiresolution_filter.py