Add Support for multiple scopes in database configuration

Currently, in Sync Gateway version 3.1, we support only one scope per database. If needed, multiple databases can be created to serve different scopes.

However, this can have limitations:

• This will require different sets of users.
• Even if the above limitation is doable, the concern now is that, from the Couchbase Lite perspective multiple replicators (one per bucket/scope) will be needed to sync multiple scopes. Therefore, that means opening multiple connections. This may impact the performance of the app.

Thus, we should add support for multiple multiple scopes in database configuration.