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.~~
Freetype and our renderer has no problem with those kind of glyphs.  The only issue is that the gnu freefonts don't include glyphs for them.

We shouldn't be hacking those symbols into the title anyway though - they should be displayed as images in their own row below the title, with tooltips that describe what each icon represents.