Applications as python modules

https://github.com/KratosMultiphysics/Kratos/pull/3217/ enables the applications can be used as python-modules.

This requires the following adaptations: (using the StructuralMechanicsApplicaiton as example). Only two files have to be modified.

1. Moving the StructuralMechanicsApplication.py from the root-folder into python_scripts and renaming to __init__.py

2. In this file add a second dot . for importing the application_importer:

   • from: from . import application_importer
   • to: from .. import application_importer

3. Also in this file, add the __path__ to the call of ImportApplication:

   • from: application_importer.ImportApplication(application,application_name,application_folder,caller)
   • to: application_importer.ImportApplication(application,application_name,application_folder,caller, __path__)

4. In CMakeLists.txt: Change the location where the __init__.py (formerly StructuralMechanicsApplication.py) is being installed to:

   • from: install(FILES "${CMAKE_CURRENT_SOURCE_DIR}/StructuralMechanicsApplication.py" DESTINATION KratosMultiphysics )
   • to install(FILES "${CMAKE_CURRENT_SOURCE_DIR}/python_scripts/__init__.py" DESTINATION "KratosMultiphysics/StructuralMechanicsApplication")

This results in the following structure in the KratosMultiphysics-Folder:

previously:

KratosMultiphysics
 |-- __init__.py
 |-- application_importer.py    
 |-- kratos_globals.py
 |-- ... (other kratos files)
 |-- StructuralMechanicsApplication.py

new:

KratosMultiphysics
 |-- __init__.py
 |-- application_importer.py    
 |-- kratos_globals.py
 |-- ... (other kratos files)
 |-- StructuralMechanicsApplication
      |-- __init__.py