Volume control

There was implemented microphone muting for calls. Volume control is not ready yet
![1](https://cloud.githubusercontent.com/assets/2827204/3970130/501eb1ba-27c7-11e4-8425-ac587e25754e.png)
![2](https://cloud.githubusercontent.com/assets/2827204/3970136/59e3a3a4-27c7-11e4-9321-5630629d4173.png)