Description:
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Implement SolrResponse::getArrayResponse() to return array version of the Solr Server Response for any response writer.

Test script:
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// instance of Solrclient
$client->setResponseWriter($responseWriter);
$q = new SolrQuery("lucene");
$response = $client->query ( $q );
$arrayResponse = $response->getArrayResponse();
var_dump(is_array($arrayResponse));

Expected result:
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bool(true)