PDAL OCI reader needs a different connection method for GRiD / Greyhound integration

The OCI connection currently uses an standard Oracle connection string passed in the pipeline. For security, when passing pipelines, perhaps we could add a file reference to the connection string. This would allow the pipeline to work using the same connection method internally (OCI) but externally use a Basic Auth URL from GRiD that returns a pipeline to Greyhound that contains a file reference for PDAL to get the OCI connection info.