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.~~
Rather than colours i'd like to see little icons or something like that.