Removes sample app Core

deleted:    core/__init__.py
deleted:    core/models.py
deleted:    core/templates/404.html
deleted:    core/templates/500.html
deleted:    core/templates/hello-world.html
deleted:    core/tests.py
deleted:    core/urls.py
deleted:    core/views.py
modified:   settings.py
modified:   test.sh