Success and Error notifications in the designer

Added "success" and "error" notifications to the designer.

**Sample**
![image](https://cloud.githubusercontent.com/assets/25212/4396252/4a4a88bc-4433-11e4-9e4c-3e940d46b125.png)

STT
* Save an app to see a Success notification
* Save As an app with the same name as an existing app to see an Error notification

Fixes #2107