Google Cast ready plugin

Hi,

After the release of the final SDK for Chromecast, Google has made many changes in their guidelines.
I propose this pull request to meet the requirements by Google.

- icon has changed, only visible if Chromecast receiver detected, turns blue while casting
- custom media tech to control remote device
- launch, stop, play, pause, seek and volume control implemented
- back to local player enabled
- Google Cast ready plugin

![screen1](https://f.cloud.github.com/assets/1327753/2213781/2e56e902-99c5-11e3-8bdf-9f1df1815db5.png)
![screen2](https://f.cloud.github.com/assets/1327753/2213782/2e5a4bb0-99c5-11e3-91d1-6a709873cd5e.png)