Damaged by terrain

This is a trait that replaces the PoisonedByTiberium trait for a more general approach, this now not only works on resources but also on terrain, have a unit that cant live on anything but tiberium add Clear and Beach to the Terrain variable (you might need to add Rough too but I have no idea what terrain that is).
This has to be `Rock`. You currently broke the feature:

![image](https://cloud.githubusercontent.com/assets/756669/5422846/5981d858-829a-11e4-8795-8196fb2b7acf.png)