Call duration label

![call3](https://cloud.githubusercontent.com/assets/2544251/4877951/57bf0396-62fc-11e4-9c03-1a9cab01bac1.png)
![call4](https://cloud.githubusercontent.com/assets/2544251/4877954/6aa424e6-62fc-11e4-896c-d2facc67d091.png)

I also added some qDebug messages, please don't remove them, I'll need them soon.
Yes because your timer variable is uninitialized (ie. has some random value != nullptr). Add timer(nullptr) to the constructor.