more subtle kernel indicator

fix @jasongrout complaint on ML.

<del>Filled circle are not availlable until we update font awesome to v4.</del>

![capture decran 2014-01-21 a 16 13 28](https://f.cloud.github.com/assets/335567/1964473/06f3f766-82ae-11e3-827d-f54bc631f506.png)
![capture decran 2014-01-21 a 16 13 35](https://f.cloud.github.com/assets/335567/1964474/06f97470-82ae-11e3-9923-17edbee91dcd.png)

It uses Pause, Play, Stop, Refresh icons for Idle, Busy, Interupting and Restart.

This right now Hack and extend the "Notification" API, we could have an "Indicator" api for purely static things only with icons.