Display audio properties + Album year + widget with stop button + robustness

- Add display audio properties (codec, bitrate, sample size, sample frequency) with configuration do enable it
- Add display album year and configuration to enable it
- Add widget with stop button
- Robustness fix for streams with empty tags

![screenshot-mpdroid-nowplaying](https://f.cloud.github.com/assets/1272343/1366704/5a361b44-38de-11e3-8c71-f5f9ad4c728d.png)
![screenshot-mpdroid-preferences](https://f.cloud.github.com/assets/1272343/1366705/5a639c90-38de-11e3-97ee-81b11fa5247f.png)
![screenshot-mpdroid-widget](https://f.cloud.github.com/assets/1272343/1366706/5a660ff2-38de-11e3-86b4-0a1f27501072.png)