[dbmanager] messagebox => messagebar

it looks as below:

![schermata del 2014-09-17 17 23 42](https://cloud.githubusercontent.com/assets/1374682/4306362/5471806a-3e80-11e4-97d7-18095b971666.png)

@slarosa I'd say all these "Sorry" headings should be removed. They're not required and just like clumsy.