Security App is not really following the app pattern.

• does not have a main sub app but 4 "same level" ones
  -> has to code opening of all subapps on startup
• does not offer a way to re-open a sub app once it has been closed

We should either split security app into several apps or create a main subapp that allows opening/closing of other sub apps. Then we could also directly use ContentApp instead of having to define proper SecurityApp (only adds opening of the sub apps) because of the above problems:

        getAppContext().openSubApp(new DefaultLocation(Location.LOCATION_TYPE_APP, "security", "systemUsers", "/system"));
        getAppContext().openSubApp(new DefaultLocation(Location.LOCATION_TYPE_APP, "security", "groups", ""));
        getAppContext().openSubApp(new DefaultLocation(Location.LOCATION_TYPE_APP, "security", "roles", ""));
        getAppContext().openSubApp(new DefaultLocation(Location.LOCATION_TYPE_APP, "security", "users", "/admin"));