Overhaul the observer sidebar.

![replay](https://cloud.githubusercontent.com/assets/167819/4605336/3c9abe9c-51dc-11e4-99ff-3ad5ed43483a.png)

This updates the RA observer sidebar to match the new theme, and adds a 200% playback speed option to all four mods.
This should be using the regular cast operator, since we'll get a nicer InvalidCastException at the point of failure instead of a vague-ish NullReferenceException at the next line.