Color coded the server browser and added a filter for password protected games

This implements #4495 and applies the color code style from www.openra.net/games/ with a legend:

![image](https://cloud.githubusercontent.com/assets/756669/5157404/c3e91e68-7309-11e4-9c5c-22fa5eface1e.png)

Essentially a followup of https://github.com/OpenRA/OpenRA/pull/6983 whose game name + "(Password)" was a little too subtle and unpolished for my taste.
Hardcoding these is bad news for mods that define their own custom UI. These colours may not work with whatever background colours the mod uses.