Fixed #179 add Flask-Caching

src/covid19/blueprints/app_admin/app_admin_views.py

src/covid19/blueprints/app_all/all_views.py

src/covid19/blueprints/ecdc/ecdc_service.py

src/covid19/blueprints/ecdc/ecdc_views.py

src/covid19/blueprints/ecdc_test/ecdc_test_service.py

src/covid19/blueprints/intensivregister/divi_service.py

...ovid19/blueprints/intensivregister/divi_service_update.py

src/covid19/blueprints/intensivregister/divi_views.py

...d19/blueprints/intensivregister_test/divi_test_service.py

...vid19/blueprints/intensivregister_test/divi_test_views.py

src/covid19/blueprints/owid/owid_service.py

src/covid19/blueprints/owid/owid_views.py

src/covid19/blueprints/owid_test/owid_test_service.py

src/covid19/blueprints/rki_cases/rki_service.py

src/covid19/blueprints/rki_cases/rki_views.py

src/covid19/blueprints/rki_cases_test/rki_test_service.py

...d19/blueprints/rki_vaccination/rki_vaccination_service.py

...vid19/blueprints/rki_vaccination/rki_vaccination_views.py

src/covid19/blueprints/who/who_service.py

src/covid19/blueprints/who/who_service_update.py