Set scijava.app.directory property

So that fiji.cfg is written with a relative path.

Author: ctrueden

src/main/java/net/imagej/ui/swing/updater/LauncherMigrator.java

@@ -328,6 +328,7 @@ private void switchToNewLauncher() {
 		}
 
 		setPropertyIfNull("scijava.app.name", appTitle);
+		setPropertyIfNull("scijava.app.directory", appDir.getPath());
 
 		Path splashImage = appDir.toPath().resolve("images").resolve("icon.png");
 		setPropertyIfNull("scijava.app.splash-image", splashImage.toString());