Selection outline

Buildings now show a white outline border when selected (as per #63).

That enables us to use a custom shader for player colors. As you can see on the picture
![image](https://f.cloud.github.com/assets/985892/2241817/d246a6b0-9ce5-11e3-8f93-438c05081ad5.png)

Right now the player colour is fixed but this should be made configurable so every player can have their own colour, it also makes the city look more consistent in my opinion.


Also, #130 is fixed (you can now click on any part of the building to select it, this was especially annoying with the hellenic market and others).