implemented highlighting of tiles on action edit

src/main/java/de/srsoftware/web4rail/actions/SetDisplayText.java

@@ -29,6 +29,12 @@ public class SetDisplayText extends TextAction{
 		return true;
 	}
 	
+	@Override
+	protected String highlightId() {
+		return isSet(display) ? display.id().toString() : null;
+	}
+	
+	
 	@Override
 	public JSONObject json() {
 		JSONObject json = super.json();