Hide settings/apps unless apps:true is in config.js

fixes #3031

- Adds an initializer for passing config to the frontend, it's not pretty but it works
- Forwards the apps route and hides the apps menu item if apps:true is not present in config.js
Since `showApps` just checks for config itself and the config initializer also puts it in the route, I think you can just do a `!this.get('config.apps')` here?