Allow users to maintain a JSON database in the app

[aeberhart]

We often have apps that ship with a fixed database. We typically include a SQLite DB in the app for this. The downside of this is that the DB file is binary and cannot be edited easily.

We could allow a JSON DB to be provided by the user:

• define which tables & columns are available via a JSON schema
• the data can be stored in the model folder
• keep it logically separate from the config DB, since config often has special handling (filtered out etc...)