[Bug] Server type return in HTTP header is not Corese

[MaillPierre]

Issue Description:

The server type return in the HTTP header of SPARQL query responses is not related to Corese

Steps to Reproduce:

1. Create an empty file "test.ttl"
2. Create a query file "query.rq" containing:

SELECT DISTINCT ?server ?serverGet {
    SERVICE <https://corese.inria.fr/sparql?mode=report> {
        {
            SELECT * {
                ?s ?p ?o
            } LIMIT 1
        }
    }
    values (?_service_report_0 ){
        (UNDEF )
    }
    BIND( js:server() AS ?server)
    BIND( xt:get(?_service_report_0, "server") AS ?serverGet)
}

3. Use Corese-command such as java -jar corese-command-4.5.0.jar sparql -i test.ttl -q query.rq -o result.csv -of csv
4. Server type appears in result.csv

Expected Behavior:

A result with a relation to Corese is expected, such as:

server,serverGet,_service_report_0
corese,corese/4.5.0,_j_4

Actual Behavior: The result obtained are related to the NGinx web server:

server,serverGet,_service_report_0
nginx,nginx/1.12.1,_j_4

Note to Developers:

The headers should probably be adapted depending on the response data type requested. text/html could still return NGinx, but any RDF-related type should indicate the type of SPARQL server.