fix panel styling

1: Scrollbars were always showed, making the panel look ugly, especially in dark mode
2: The panel contents were too close to the edge of the panel and looked a bit off
3: The status bar does not cover the panel's contents even without the bottom padding

![before](https://cloud.githubusercontent.com/assets/1592427/5547204/30e23e3e-8b5e-11e4-85fc-b5dde3c5bc27.png)

![after](https://cloud.githubusercontent.com/assets/1592427/5547206/398b0584-8b5e-11e4-8f1d-90da5d2bd914.png)

PS: As you can see this does not fix all of the issues, just some of them.

PPS: I can submit those as separate PRs should you prefer so.