Store forum config in DB

[Lanny]

In a dockerized production environment, rebuilding images to change settings is a bad idea. Even outside of dockerization, editing the setting file and bouncing the server isn't ideal and not very user friendly to admins.

The idea here is to store the config in the DB and create a form for editing it. This requires that the ConfigurationManager be able to reload. Hitting the DB for each .get_config() call isn't acceptable so the manager will need to cache internally and invalidate periodically or consult a shared cache to know when to invalidate.