added toString

usgs-api/src/main/java/de/potsdam/gfz/usgsapi/json/datamodels/InventoryScene.java

@@ -71,4 +71,8 @@ public class InventoryScene {
 	 */
 	public String		summary;
 
+	@Override
+	public String toString() {
+		return "entityid(" + entityId + "), acquisitiondate(" + acquisitionDate + "), summary(" + summary + ")";
+	}
 }