Overhaul observer shroud selector.

The list is now divided into teams, and includes faction and color.
This adds hotkeys (replacing control groups for observers) of 0-9 to cycle teams (+shift to cycle in reverse), and -/= for combined/no shroud (these are configurable in the options).

![shroudview](https://f.cloud.github.com/assets/167819/2490406/a54e82aa-b1a7-11e3-95ab-798115334255.png)