Implements NOISSUE: Rename error to fix validation error over field label on Configuration Step

Sign-off: @mumia 

Before:
![screen shot 2014-01-02 at 09 56 36](https://f.cloud.github.com/assets/74459/1831615/da8043e6-7395-11e3-9539-87f8561688ed.png)

After: 
![screen shot 2014-01-02 at 10 08 09](https://f.cloud.github.com/assets/74459/1831616/e1743888-7395-11e3-801c-8384436fc857.png)

To solve this issue, I just renamed some error messages, to keep the same message to all fields.