Refactoring: rename covid19 to flask_covid19

src/flask_covid19/__init__.py

src/flask_covid19/blueprints/app_admin/app_admin_views.py

src/flask_covid19/blueprints/app_all/all_views.py

src/flask_covid19/blueprints/app_user/user_views.py

src/flask_covid19/blueprints/app_web/__init__.py

...covid19/blueprints/app_web/application_model_transient.py

src/flask_covid19/blueprints/app_web/application_service.py

src/flask_covid19/blueprints/app_web/application_views.py

.../app_application/fragments/fragment_flashed_messages.html

...plates/app_application/fragments/fragment_pagination.html

...app_web/templates/app_application/layout/page_layout.html

...web/templates/app_application/layout/page_layout_old.html

.../app_web/templates/app_application/navigation/navbar.html

...app_web/templates/app_application/navigation/navtabs.html

...ueprints/app_web/templates/app_application/page_home.html

src/flask_covid19/blueprints/divi/divi_test_views.py

src/flask_covid19/blueprints/divi/divi_views.py

src/flask_covid19/blueprints/divi_test/templates/__init__.py

src/flask_covid19/blueprints/ecdc/ecdc_test_views.py

src/flask_covid19/blueprints/ecdc/ecdc_views.py