In tab "Tree" of Faces Config Editor you can add follow elements to node "Application":
1. Message Bundle
2. Resource Bundle
3. EL Resolver
4. Property Resolver
5. Variable Resolver
6. Extension

All of them are shown as child nodes for node "Application" but Message Bundle
It is not logical.
The main problem is that if you add "Message Bundle" to "Application" you can not see the result of your action.