Added Urban Terrain Expansion

Horray for the picturesque old town construction set made by @CombineCR!

![image](https://f.cloud.github.com/assets/756669/784465/a66485e0-ea65-11e2-9e31-8d0aa3a0bc86.png)

[Urban Terrain Expansion](http://www.sleipnirstuff.com/forum/viewtopic.php?f=83&t=16117)