Disposable: make dispose() do nothing by default

Already, the abstract service layer did that. May as well generalize it.

Author: ctrueden

src/main/java/org/scijava/Disposable.java

@@ -42,6 +42,7 @@ public interface Disposable {
 	 * Performs any needed cleanup of the object's services, in preparation for
 	 * the object being retired (e.g., to make garbage collection possible).
 	 */
-	void dispose();
-
+	default void dispose() {
+		// NB: Do nothing by default.
+	}
 }

src/main/java/org/scijava/service/AbstractService.java

@@ -74,13 +74,6 @@ public void setContext(final Context context) {
 		this.context = context;
 	}
 
-	// -- Disposable methods --
-
-	@Override
-	public void dispose() {
-		// NB: Do nothing by default.
-	}
-
 	// -- Object methods --
 
 	@Override