Resolve some deprecated API usage warnings

Author: tkuhn

src/main/java/org/nanopub/CustomTrigWriter.java

@@ -39,7 +39,7 @@ public CustomTrigWriter(Writer writer, Set<String> usedPrefixes) {
 	}
 
 	public CustomTrigWriter(Set<String> usedPrefixes) {
-		super(NullOutputStream.NULL_OUTPUT_STREAM);
+		super(NullOutputStream.INSTANCE);
 		this.usedPrefixes = usedPrefixes;
 	}
 

src/main/java/org/nanopub/extra/server/FetchIndex.java

@@ -255,10 +255,6 @@ public RegistryInfo getLastRegistry() {
 			return lastRegistry;
 		}
 
-		public void ignoreServer(RegistryInfo r) {
-			registries.add(r);
-		}
-
 		public void prepareForTryingServer(RegistryInfo r) {
 			registries.add(r);
 			lastRegistry = r;

src/main/java/org/nanopub/trusty/TrustyNanopubUtils.java

@@ -6,23 +6,22 @@
 import java.nio.charset.Charset;
 import java.util.List;
 
-import net.trustyuri.TrustyUriUtils;
-import net.trustyuri.rdf.RdfHasher;
-import net.trustyuri.rdf.RdfPreprocessor;
-import net.trustyuri.rdf.RdfUtils;
-import net.trustyuri.rdf.TransformRdfSetting;
-
-import org.nanopub.Nanopub;
-import org.nanopub.NanopubUtils;
 import org.eclipse.rdf4j.model.Statement;
 import org.eclipse.rdf4j.rio.RDFFormat;
 import org.eclipse.rdf4j.rio.RDFHandlerException;
 import org.eclipse.rdf4j.rio.RDFWriter;
 import org.eclipse.rdf4j.rio.Rio;
+import org.nanopub.Nanopub;
+import org.nanopub.NanopubUtils;
+
+import net.trustyuri.TrustyUriUtils;
+import net.trustyuri.rdf.RdfHasher;
+import net.trustyuri.rdf.RdfPreprocessor;
+import net.trustyuri.rdf.TransformRdfSetting;
 
 public class TrustyNanopubUtils {
 
-	public static RDFFormat STNP_FORMAT = new RDFFormat("Serialized Trusty Nanopub", "text/plain", Charset.forName("UTF8"), "stnp", false, true);
+	public static RDFFormat STNP_FORMAT = new RDFFormat("Serialized Trusty Nanopub", "text/plain", Charset.forName("UTF8"), "stnp", false, true, false);
 
 	private TrustyNanopubUtils() {}  // no instances allowed