Initial configuration implementation

* Pub/Sub mechanisme via Postgres listen/notify
* Caching of configs + invalidation over pub/sub
* Getting / Updating configs
The config row will be in the database as the trigger executes before it returns back to node when creating the app. That said, the app's cache might still be stale by the time the getConfig request comes in. It's pretty unlikely, but it could happen.

I'll stick a config listener in the createApp utility, that should take care of any possible intermittent failures