Improved guide GUI

I've improved the scroll panel, so it doesn't fight for control with the scroll bar when scrolling with the mouse. It's now the size it should be, as previously you could scroll with the mouse to the right of the GUI screen.

Before:
![2014-02-07_12 25 58](https://f.cloud.github.com/assets/3743378/2109825/a08487d2-8ff7-11e3-94a5-fc7f0772cc7a.png)

After:
![2014-02-07_12 48 36](https://f.cloud.github.com/assets/3743378/2109826/a087e7ce-8ff7-11e3-93d6-803a4249ab46.png)

(The red overlay is just to see the size of the panel)

I've also added some overlays on top of the panel, so when scrolling with the mouse/scroll bar it will look a lot smoother and text will not pop in at the top/bottom of the scroll panel.