Volume controller

This PR adds two SeekBars to control the volume and the screen brightness. 

It also updates the demo application to show how multitouch gestures can be detected and used in order to update those seekbars.

![device-2014-10-11-122048](https://cloud.githubusercontent.com/assets/531613/4602526/7c9e0f96-513f-11e4-91ec-875b40b53723.png)