Added icons to social community web resources

The header got kinda bloated so I moved the external links elsewhere with pretty iconography:

![social-icons](https://f.cloud.github.com/assets/756669/303846/bf055984-962e-11e2-996e-f51be824de32.png)

also completed the collection because unlike the abandoned Twitter/Facebook accounts OpenRA is quite popular on DesuraNET websites nowadays.