Support setting the schema in the configuration file

[fwgreen]

Database tables are automatically placed in the default public schema during preparation. This could be a problem if one doesn't control the database.

{
    "host": "127.0.0.1",
    "user": "postgres",
    "password": "",
    "database": "test",
    "schema": "test-schema",
    "port": 5432
}