Add convolution and mean filtering

src/main/java/app/INavigator.java

@@ -10,6 +10,7 @@ public interface INavigator {
      * Displays Fourier view
      */
     void showFourier();
-    void showFiltering();
+    void showIdealFiltering();
     void showButterworth();
+    void showConvolutionFiltering();
 }