Add key change controls to ingame menu

![minetestck](https://f.cloud.github.com/assets/1996449/255698/8b313990-8c13-11e2-9094-44049400f13d.png)
![minetestckm](https://f.cloud.github.com/assets/1996449/255701/8b618712-8c13-11e2-84d1-8101a6f2e3e1.png)
![minetestckig](https://f.cloud.github.com/assets/1996449/255699/8b60031a-8c13-11e2-9e96-c33fb2171d31.png)
![minetestckcpig](https://f.cloud.github.com/assets/1996449/255702/8b935cce-8c13-11e2-9546-71580029fe4a.png)
![minetestckmig](https://f.cloud.github.com/assets/1996449/255700/8b603826-8c13-11e2-9e6c-78a5048fc885.png)