A client of high-level SchemaProxy may want to know whether a schema
is a reference and the name of the reference. This information is
available from methods GetSchemaReference() and IsSchemaReference()
in low-level SchemaProxy. Provide a GoLow() method to retrieve the
low-level SchemaProxy for a high-level SchemaProxy.
A feature request from Travis Newhouse to make it easier to know which primitives have been set, and which have not. defaulting everything to 0 or false just doesn't work so well.