Use css for testing retina support

src/main/java/io/bitsquare/gui/bitsquare.css

@@ -20,6 +20,9 @@ lower gradient color on tab: dddddd
     -bs-bg-grey: #dddddd;
 }
 
+#splash-logo {
+    -fx-image: url("../../../images/logo_splash.png");
+}
 
 /* Splash */
 #splash {

src/main/java/io/bitsquare/gui/main/MainViewCB.java

@@ -269,9 +269,9 @@ public class MainViewCB extends ViewCB<MainPM> {
         vBox.setSpacing(10);
         vBox.setId("splash");
 
-        ImageView logo = ImageUtil.getIconImageView(ImageUtil.SPLASH_LOGO);
-        logo.setFitWidth(300);
-        logo.setFitHeight(300);
+        //ImageView logo = ImageUtil.getIconImageView(ImageUtil.SPLASH_LOGO);
+        ImageView logo = new ImageView();
+        logo.setId("splash-logo");
 
         Label subTitle = new Label("The decentralized Bitcoin exchange");
         subTitle.setAlignment(Pos.CENTER);