Massive code cleanup

- Avoid fighting import cycles using a factory function
- Collapse useless subpackages into simple modules
- Move flask plugins / infrastructure in own module
- Refactor how blueprints are used to localize information about
  URL routing to app factory

docker/entrypoint.sh

@@ -1,3 +1,2 @@
 #!/bin/sh
-
-exec hypercorn -b "0.0.0.0:8000" snikket_web:app
+exec hypercorn -b "0.0.0.0:8000" 'snikket_web:create_app()'