Support for Layer 0 databases requiring authentication

[BA-MBSE]

Need to add support or guidance for databases at Layer 0 which require authentication
For example, MarkLogic database sparql and graph endpoints are implemented via REST and require authentication via headers

[dlamoris]

Based on discussion during dev tagups, this is akin to an app needing a postgres username/pass to connect to a postgres db, and not individual user authentication to layer0 db. A common solution would just be for us to add 1 or more optional application properties as configuration so those would be added as headers to all sparql communication with the triplestore.