Progress on updating the (dataset) operator to load default graphs into the repository using their graph names, and specify the default graphs as using a default match, rathern than a named match, so that the specific "named" graphs will match as either/or default (meaning context == false) or named (meaning context == IRI or variable).
Implement datasets through unions and filters over specified graphs by re-writing the query. Still fails dataset-012b
Revert Gitfile use of local version of rdf.
Simplify dataset diagnostic messages.