Remove unused GPL-licensed code

For unknown reasons, in 2009 several files from the JDK were copied into
the Dataverse codebase, instead of referenced.
It appears that these classes weren't really used.

src/main/java/edu/harvard/iq/dataverse/ingest/metadataextraction/spi/FileMetadataExtractorSpi.java

@@ -10,9 +10,7 @@
 import java.util.logging.*;
 import java.io.*;
 
-import edu.harvard.iq.dataverse.ingest.plugin.spi.RegisterableService;
 import edu.harvard.iq.dataverse.ingest.plugin.spi.IngestServiceProvider;
-import edu.harvard.iq.dataverse.ingest.plugin.spi.ServiceRegistry;
 import java.nio.MappedByteBuffer;
 import java.util.Locale;
 
@@ -44,22 +42,6 @@ public FileMetadataExtractorSpi(String vendorName, String version) {
         this.version = version;
     }
 
-    public void onRegistration(ServiceRegistry registry,
-                               Class<?> category) {}
-
-
-    public void onDeregistration(ServiceRegistry registry,
-                                 Class<?> category) {}
-
-    public String getVersion() {
-        return version;
-    }
-
-    public String getVendorName() {
-        return vendorName;
-    }
-
-
     public abstract String getDescription(Locale locale);
 
     protected String[] names = null;

src/main/java/edu/harvard/iq/dataverse/ingest/plugin/spi/IngestServiceProvider.java

@@ -29,7 +29,7 @@
  * 
  * @author akio sone at UNC-Odum
  */
-public abstract class IngestServiceProvider  implements RegisterableService {
+public abstract class IngestServiceProvider  {
 
     /**
      * The name of the vendor that is responsible for coding this
@@ -62,29 +62,6 @@ public IngestServiceProvider(String vendorName, String version) {
     public IngestServiceProvider() {
     }
 
-    /**
-     * A callback to be called exactly once after this Spi class
-     * has been instantiated and registered in a 
-     * <code>ServiceRegistry</code>.
-     *
-     * @param registry the ServiceRegistry instance.
-     * @param category a <code>Class</code>  object that indicatges
-     * its registry category under which this object has been registered.
-     * category.
-     */
-    public void onRegistration(ServiceRegistry registry,
-                               Class<?> category) {}
-
-    /**
-     * A callback whenever this Spi class is deregistered from
-     * a <code>ServiceRegistry</code>.
-     *
-     * @param registry the ServiceRegistry instance.
-     * @param category a <code>Class</code> object that indicatges
-     * its registry category from which this object is being de-registered.
-     */
-    public void onDeregistration(ServiceRegistry registry,
-                                 Class<?> category) {}
     /**
      * Gets the value of the version field.
      *