Set MySQL as standard database

MySQL installed:
![-dvj](https://f.cloud.github.com/assets/878997/405826/5ca79c66-aa15-11e2-9fa4-f3f6f8c6774a.png)

MySQL is not installed:
![dsqz](https://f.cloud.github.com/assets/878997/405827/6b9847de-aa15-11e2-8820-3f9cc7b5ae63.png) 

Ref #3046 

\cc @karlitschek @Raydiation @jancborchardt