Ensure all core services implement SciJavaService

This commit also adds a test to prevent this issue in the future.

Author: ctrueden

src/main/java/org/scijava/app/AppService.java

@@ -34,13 +34,14 @@
 import java.util.Map;
 
 import org.scijava.plugin.SingletonService;
+import org.scijava.service.SciJavaService;
 
 /**
  * Interface for application-level functionality.
  * 
  * @author Curtis Rueden
  */
-public interface AppService extends SingletonService<App> {
+public interface AppService extends SingletonService<App>, SciJavaService {
 
 	/** Gets the foremost application (the one with the highest priority). */
 	App getApp();

src/main/java/org/scijava/convert/ConvertService.java

@@ -35,6 +35,7 @@
 import java.util.Collection;
 
 import org.scijava.plugin.HandlerService;
+import org.scijava.service.SciJavaService;
 
 /**
  * Service for converting between types using an extensible plugin:
@@ -46,8 +47,9 @@
  * @author Mark Hiner
  */
 public interface ConvertService extends
-	HandlerService<ConversionRequest, Converter<?, ?>>
+	HandlerService<ConversionRequest, Converter<?, ?>>, SciJavaService
 {
+
 	/**
 	 * @see Converter#convert(Object, Type)
 	 */

src/test/java/org/scijava/service/ServiceIndexTest.java

@@ -34,6 +34,7 @@
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
 
 import java.util.List;
 
@@ -66,6 +67,14 @@ public void testGetAll() {
 		assertSame(StderrLogService.class, all.get(3).getClass());
 	}
 
+	@Test
+	public void testMarkerInterfaces() {
+		final Context context = new Context();
+		for (Service s : context.getServiceIndex().getAll()) {
+			assertTrue(s.getClass().getName(), s instanceof SciJavaService);
+		}
+	}
+
 	/**
 	 * Test the {@link ServiceIndex#getPrevService(Class, Class)} operation.
 	 */