Add Address Tool to "Add Fixture" dialog as a way to enter the channel

Add a button next to the address spin in the "Add Fixture" dialog that can be clicked
to display the required DIP switch configuration for the given address or to change
the address by modifying the sliders positions.
Once again, I think this makes it easier to enter a given configuration if you don't know binary, or to look at the slider's positions right when entering them.

![bildschirmfoto vom 2014-04-27 12 17 05](https://cloud.githubusercontent.com/assets/1311964/2810961/537796a4-cdf6-11e3-81d4-aaa9833b42cf.png)


![bildschirmfoto vom 2014-04-27 12 17 36](https://cloud.githubusercontent.com/assets/1311964/2810960/53776de6-cdf6-11e3-84bf-6e084b4234d5.png)