Can't import named graphs

[lecoqlibre]

When trying $connector->import("./path/to/jsonld"), the import fails if the @graph has an associated @id.

Named graphs are ignored by the sweetrdf/easyrdf library (required by Semantizer) at this line: https://github.com/sweetrdf/easyrdf/blob/da4d8bfe6d6eb54564869d34826a4c6f4d0a67c5/lib/Parser/JsonLd.php#L85.

The connector/semantizer should raise an Exception when encountering named graphs.

The taxonomy export should not contain named graph.