Poisoned 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).
1) I don't see a `SafeTerrain` field anywhere
2) Comments should be descriptive/action-y, not a narrative/dialog