JFX: Allow AF3PartView subclass access to the controller

Issue-Ref: 3541
Issue-Url: https://af3-developer.fortiss.org/issues/3541


Signed-off-by: Alexander Diewald <diewald@fortiss.org>

org.fortiss.tooling.common.ui/src/org/fortiss/tooling/common/ui/javafx/.ratings

-AF3FXViewPart.java 3e4510f9e9f86ecf5ba29432342acd50e030aaaa GREEN
+AF3FXViewPart.java af974e21c086a86134d4b2d6cdf9da1a31aea7de YELLOW

org.fortiss.tooling.common.ui/src/org/fortiss/tooling/common/ui/javafx/AF3FXViewPart.java

@@ -49,7 +49,7 @@ public abstract class AF3FXViewPart extends FXViewPart {
 	private Pane root;
 
 	/** Specifies the view part's layout and logic. */
-	private ICompositeFXController<? extends Node, ? extends Node> controller;
+	protected final ICompositeFXController<? extends Node, ? extends Node> controller;
 
 	/**
 	 * Constructor. Allows to pass the view's FXML definition file.